Title:
CONTROL SYSTEM FOR AUDIO-VISUAL DEVICES CONNECTED BY CABLES
United States Patent 3691528


Abstract:
A system for controlling any of a plurality of information storage or generating devices which are grouped in operative association with common connectors along a cable common thereto by any of a plurality of remote stations which are also grouped in operative association with common connectors along a common cable. Means are provided for generating from a station a signal representative of a device address to transfer such signal to each of the devices. Means are provided for comparing the generated signal with device addresses registered in association with the devices whereby, upon identity therebetween, control of the device is effected to the generating station first to request such control. Feedback means are provided operative with the generating station and other stations to indicate the status of the device and its function, and to indicate when control thereof has been relinquished. Means enabling an overriding control station are also provided.



Inventors:
Calvagna, James F. (Anaheim, CA)
Balling, Roger A. (Santa Ana, CA)
Application Number:
05/028698
Publication Date:
09/12/1972
Filing Date:
04/15/1970
Assignee:
COMMUNITY BANK
Primary Class:
Other Classes:
340/3.54, 340/3.7, 340/4.37, 340/9.15, 340/10.6, 340/12.52
International Classes:
G09B5/12; (IPC1-7): H04Q3/00; H04Q5/00
Field of Search:
340/152R,147LP
View Patent Images:



Primary Examiner:
Pitts, Harold I.
Claims:
What is claimed is

1. A system for control of any of a plurality of audio-visual sources by any of a plurality of remote stations, comprising:

2. The system of claim 1 wherein said signal generating means comprises means for generating a binary code decimal signal of predetermined number of decimals, said cable comprising at least as many separate electrical conductors as required to define one binary code decimal digit.

3. The system of claim 1 including means for generating programmed signals in first binary code decimals of predetermined number of decimals for commanding data to be transmitted and means for generating data signals in second binary code decimals of predetermined number of decimals in representation of data to be transmitted.

4. The system of claim 3 including means for generating a strobe signal timed to said signal generation, and means at each of said stations and audio-visual sources responsive to said strobe signal for timing response thereto to said command or data signals.

5. The system of claim 1 including a plurality of station terminals each station terminal having means for electrically associating a predetermined plurality of said remote stations therewith and means for effecting said second common cable connection.

6. The system of claim 5 including nand logic element for each station operatively connecting said station to its connector.

7. The system of claim 1 including a plurality of audio-visual source terminal connectors, each audio-visual source terminal having means for electrically associating a predetermined plurality of said audio-visual sources therewith and means for effecting said first common cable connection.

8. The system of claim 7 wherein each audio-visual source terminal includes a plurality of connecting lines corresponding to a number of binary code decimals at least as great as required for selective connection to each audio-visual source associated therewith, said audio-visual source being selectively connected to said connecting lines in binary code format.

9. The system of claim 1 including: means operatively associated with each of said remote stations for generating a signal representative of that station's address; and

10. The system of claim 1 including means for sequentially signaling each of said plurality of stations to generate said signal.

11. The system of claim 1 including means operatively associated with at least one of said stations for generating a signal representative of a function desired to be performed by an addressed audio-visual source and means connected to said addressed audio-visual source operative upon identity of said that remote station as having generated said function signal, for effecting a performance of said function.

12. The system of claim 1 including:

13. The system of claim 12 including means for sequentially signaling each of said plurality of audio-visual sources to generate said status signal.

14. The system of claim 1 including:

15. The system of claim 14 including:

16. The system of claim 1 wherein a first station is in operative control of a first audio-visual source, and including:

17. The system of claim 1 including:

18. The system of claim 17 including:

19. The system of claim 1 further including switch means connected between said audio-visual sources and said remote stations and means for controlling said switch means to connect the intelligence signal from an addressed audio-visual source to a remote station addressing said addressed audio-visual source.

20. The system of claim 19 wherein said switch means includes sufficient input terminals to receive intelligence signals from each of said audio-visual sources and has sufficient output terminals to provide an output terminal for each remote station.

Description:
BACKGROUND OF THE INVENTION

1. Field of the Invention

The fields of art to which the invention pertains include the fields of remote and digital control of equipment capable of storing information for later retrieval or for generating information for immediate use and/or recording for later retrieval.

2. Description of the Prior Art

It is often desirable to provide remote station control for audio and/or visual equipment so as to enable any one of a plurality of remote stations to either monitor or control such equipment. By the term audio and/or visual equipment it is intended to mean any apparatus capable of replaying previously recorded information in presently usable form, e.g., tape playback of audio and/or visual signals, or any apparatus capable of generating information in presently usable form which information may be currently used and/or recorded, e.g., video camera and/or microphone. Hereafter such apparatus will be referred to as "A/V" equipment, apparatus, device or source. For example, in a modern school environment, it is often desirable to allow students to have remote access to tape recordings of a variety of lessons, or to view slides or motion picture presentations via video relay, or the like. In libraries, it may be desirable to provide access at various remote stations to information recorded on magnetic tape at a variety of source locations. A number of similar or analogous systems are presently being utilized in industry and it is projected that many more such systems will be utilized in the future.

The installation and utilization of such systems can be relatively simple where only a few sources of information and a few remote stations are involved. However, when hundreds of sources and hundreds of stations are involved, installation can be very complex and very costly. Where completely automatic control is desired, the extensive amount of cable required to interconnect the units is a large factor in the installation cost. Further, in conventional systems, generally only one remote station operates at a time and when a particular A/V device is being controlled by one station, the other stations merely receive a "busy" signal requiring them to re-initiate a request for control when the line is not busy.

SUMMARY OF THE INVENTION

The present invention provides a system for digital data exchange which can be used to interconnect a very large number of remote stations to as many A/V sources such as tape recorders, live cameras, film and slide projectors etc., and can provide for remote control of these sources. In accordance with the particular system described herein, upon to 1,000 remote stations can be linked to up to 1,000 A/V devices. Importantly, all of the remote stations are linked by means of a cable which is common to the station and all the devices are linked by a cable which is common to the devices. Connectors, which can be in the form of circuit boards, can be utilized to form groups of the sources and to form groups of the stations, the connectors being coupled to the cable. A master control unit accepts incoming command signals from the remote stations and processes them for transmission of the appropriate A/V device. Additionally, status information from controlled A/V devices are transmitted over the same cable back to display indicators at the remote stations. As a result of the structuring concepts herein, a "building block" approach can be utilized to expand the capacity of the system wherein additional devices and stations can be readily accommodated. Further, the system provided herein utilizes a command structure which allows a remote station to signal for control of a presently controlled device and remain "on signal" while waiting for the initial control to be relinquished. In this respect, the master control unit is structured to query all of the stations separately and sequentially to determine whether a command has been stored at the station for transmission to the relinquished device. These functions are carried out over the same cable and connectors linking the components.

With respect to specific operation of the system, there is provided: means operatively associated with each of the A/V devices for registering an address unique to that device; means operatively associated with each of the remote stations for generating a signal representative of a device address; means for transferring generated signals between the stations and the devices; means for comparing a generated device address signal with a registered device address; and means for effecting a desired change upon identity between the signal device address and the registered device address.

Signals are generated in binary code decimals, as are other control functions, and the cable comprises as many separate electrical conductors as the total number of decimals generated. A signal is generated by the remote station which is representative of that stations address and master control means are provided for receiving both the station address signal and the device address signal for connecting that station to the device to enable that station to receive information containing signals from that device, e.g., by telemetric connection. Feedback signals are generated by the controlled device to indicate its status to the control station and other remote stations and to indicate the nature of the function of the device, if required, all over the same common cables and by means of comparison of generated signal addresses to registered signal addresses. In a particular mode of operation, a controlling station can relinquish control of a particular device by generating a signal representative thereof. A feedback signal is then generated by the controlled device which is representative of such relinquishment and which communicates this information to all remote stations monitoring that device so that any such remote station can thereafter take control. In further embodiments, a supervisory remote control station is provided having means for overriding the control of any other station and having means for effecting the control of any of the devices by any of the other stations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagramatic representation of a control system incorporating the present invention;

FIGS. 2, 3 and 4 are schematic diagrams expanding portions of the control system of FIG. 1;

FIG. 5 is a diagramatic representation of details of a control unit portion of the control system of FIG. 1;

FIG. 6 is a diagramatic representation of details of station units of the control system of FIG. 1;

FIG. 7 is a diagramatic representation of details of a terminal connected in FIG. 6;

FIG. 8 is a diagramatic representation of a manner of connecting the terminal of FIG. 7 to the station unit in FIG. 6;

FIG. 9 is a diagramatic representation of a particular station;

FIG. 10 is a diagramatic representation of source control units of the control system of FIG. 1;

FIG. 11 is a diagramatic representation of a terminal unit utilized with the source controllers of FIG. 8;

FIG. 12 is a diagramatic representation of a particular source controller; and

FIG. 13 is a diagramatic representation of a supervisor control station utilized in the control system.

DETAILED DESCRIPTION

Overall System

A remote accessible A/V system may be viewed as four separate grids:

1. Video

2. Audio

3. Device Control

4. Device Status Tallies

For closed circuit systems, these four grids may be combined into one. That is, an operator is interested in the audio, video and control of only one device at any one time. Therefore, the data relative to device selection (i.e., relating a given operator station to a given device) is sufficient to route function control signals from the station to the device, and to route device status information from the device back to the station as well as providing the audio and video signals to the station.

Irrespective of the total number of stations and devices, any station must appear to its operator as if it were the only station in the system. This means that for all intents and purposes, a selected device must behave as if it were located at the operator station. In addition, the system must never be busy for any operator. The activity at any one station must be completely independent of and have no effect on the activity at any other station.

The means of selecting and controlling a device must be simple and rapid. Device status tallies must be displayed at the station in an unambiguous and clear manner. Such considerations as color versus black and white video; sterephonic versus monophonic audio; and the wide variety of source devices (types as well as manufacturers) and monitors must not in any way hamper or proscribe the manner in which control and selection data are processed. By the same token, the system grids must not in any way determine the devices or monitors to be used. In other words, the random access and control system must be able to perform its functions irrespective of the actual A/V environment of the total system.

A further constraint is that the control system must be truly expandable. Expandable in this sense means that only the addition of equipment is necessary for a growing system. Therefore, expansion must be accomplished simply by plugging additional units into the existing system in the same manner as new Christmas tree lights are added to an existing string. At no time must expansion require the removal, modification or reworking of existing equipment.

Because of the impact of modern day computers, the access system must be computer compatible. This requires that the data exchange must be in digital format. Provisions must be included in the basic system framework for appropriate buffers for computer interface, both for inserting data into or extracting data out of the system. Both of these requirements must also be met on a manual basis. The system must include provisions for manually activated supervisory stations which can both enter or monitor data on a one at a time basis. Also means for the addition at any time of automatic tally and status displays must be provided.

The control system of the present invention may be viewed as a fixed program digital computer. Reference is now made to FIG. 1. The heart of the system is the master control unit 10 (hereinafter referred to as the MCU). Three data busses are terminated at the MCU:

1. Station Buss 11

2. A/V Switcher Buss 12

3. Source Buss 13

The station buss 11 is a six twisted pair cable, which daisy-chains from the MCU through the various station terminal chassis 14. Each station terminal chassis accommodates ten remote operator stations. Each chassis has two connectors for daisy-chaining the buss, so that as additional chassis are incorporated into an existing system by plugging into the end of the station buss. The system can accommodate up to 100 of these chassis.

The source buss 13 is similar to the station buss, a six twisted pair cable, daisy-chaining from the MCU through various source terminal chassis 16. Each chassis accommodates ten remotely controllable sources 17. Expansion is identical to the stations. Again the system can accommodate up to one hundred of these chassis.

The A/V switcher buss 14 is a ten twisted pair cable which daisy-chains through the A/V switcher chassis 18. This cable carries the control data for setting crosspoints. Each A/V switcher chassis 18 has ten inputs 19 and twenty outputs 21, audio and video. These chassis allow for expansion in both directions. For example, two chassis can provide twenty inputs by twenty outputs or ten inputs by 40 outputs. Thus, as system requirements change, the A/V switcher network can also be expanded incrementally. Irrespective of grid size, the A/V switcher buss 12 is still only a ten twisted pair cable daisy-chaining from chassis to chassis. The system can accommodate A/V switcher chassis up to its maximum configuration, one thousand inputs by one thousand outputs.

The MCU 10 is a central polling device. In turn, up to one thousand stations are scanned. As a station is scanned, all data relative to that station's status are transmitted over the station buss 11. These data are received and retransmitted over both the A/V switcher buss 12 and the source buss 13 by the MCU 10. The station operator merely enters, via a decimal keyboard, a three digit number corresponding to a desired source. After the digits have been entered a transmit button is pressed to put the station "on-line". Until the station has been put on-line, its associated terminal does not transmit when it is polled. Once on-line, the terminal transmits the station status and desired device number each time it is scanned. In addition, if the operator is pressing a function button, this is also transmitted as long as the button is held in.

After the MCU 10 has polled the stations, it polls up to one thousand sources. As each source is polled, its associated terminal transmits, via the source buss 13, its current status. These data include actual machine status (i.e., run, stop, forward, reverse, etc.) and the address of the controlling station. The MCU 10 receives the data and retransmits it over the station buss 11. All stations which are on-line, examine the data, and when a response from that source to which the station is addressed appears, the station terminal stores the associated source status word. The stored data energize the proper illuminated function push button at the remote operator station 15.

It is possible that more than one station requests a particular source. The source terminal assigns control to the first station addressing it. This causes an "ACTIVE" indicator to be illuminated at the controlling station. Subsequent stations selecting the source are placed in a monitor only status. This causes a "MONITOR" indicator to be illuminated at these stations. At all stations addressed to a particular source, the source status is displayed, but only functional commands originating at the controlling station will be obeyed by the source. Should the controlling station go off-line by pressing the cancel push button, control available is indicated to all monitoring stations, by blinking the MONITOR indicator. The first station to press the transmit push-button is then assigned control of the addressed source and all other stations automatically return to the MONITOR status. If all stations addressed to a source cancel, the source coupler automatically goes into a "park" cycle. This can be a stop, a rewind, or any desired function as determined by user requirements.

The MCU 10 contains a supervisory station. This station can assign other stations to sources, delegate control of the source as required, or take control of a source itself. In addition, it can display the status of any station or any source on a one-at-a-time, manually selected basis.

The total system scan time (complete station and source scans) is 320 milliseconds irrespective of system size. The use of station terminals as keyboard buffers, allows data entries to be made at a station without interferring with any part of the system.

The use of common data busses allows the incorporation of computer interfaces 22 and large scale system status boards as needs require. Since all system data appear on the station and source busses every 320 milliseconds, the system in effect, updates itself three times a second. Very often however, the data are unchanging over long periods of time. To provide built-in data compression for future integration into a computer system, every transmission from a station is tagged as to whether the data contained therein is in any way different from the last transmission from that station. This acts as a flag so that the computer is only alerted to data changes.

The function push-buttons at the stations, generate digital codes when pressed. These codes are interpreted by the source terminals to be machine functions. Only four machine functions are defined for remote stations:

1. Run

2. Stop

3. Forward

4. Reverse

These four functions handle all the necessary machine modes for retrieval of information. The system, however, allows for fifteen functions. The eleven unused functions can be implemented in any manner. For example, five functions (A,B,C,D,E) could be used for multiple choice testing. Two functions could be used for true/false testing. Again, since all data are present on the busses, test scoring can be implemented into the system.

The system is in effect non-existent to an operator. At no time is the system busy or overloaded. As far as the operator is concerned, he simply pushes buttons and gets immediate response. With this approach the system of the present invention can be the basic grid for a multiplicity of uses.

Referring now to FIG. 2 there is shown more in detail the station terminals and the manner in which they are connected into the system. The MCU 10 is connected by the station buss 11 to the station terminals which, as shown, may include a plurality of such terminals 25, 26, 27 up to 100 thereof. A plurality of remote control stations, in this case 10 stations, as shown generally at 28, 29 and 31, are connected to each of the station terminals 25, 26 and 27 respectively, in a manner hereinafter described so that up to 1,000 remote control stations can be provided in operative association with the station buss 11. Each of the remote stations is provided with a keyboard (not shown) for control purposes as will become clear hereinafter. As is shown at 11a, 11b and 11c, the station buss 11 is daisy-chained to each of the station terminals 25, 26 and 27. Also, if required, there may be provided a station status display apparatus 32 operative connected by a cable 33 to the station buss 11 to provide an indication of the operative status of any chosen remote station.

As is shown in FIG. 3, the MCU 10 is similarly connected by the source buss 13 to the source terminals 16 which, as shown, may include a plurality of source terminals 35, 36 and 37 up to 100 thereof. A plurality of sources, in this case 10, as shown generally at 38, 39 and 41 are connected to each source terminal 35, 36 and 37, respectively. In such manner, up to 1,000 sources can be provided. As is shown, the source buss 13 is daisy-chained at 13a, 13b and 13c to source terminals 35, 36 and 37. If desired, a source status display 42 may be provided to show the status of operation of any given source.

The system also includes a supervisor control unit for generating an overriding signal, or for assigning a particular station to a particular source, and may be connected as in the manner of a remote station, as will be further described hereinafter. An A/V switcher 24 is also provided for effecting connection between a station and a device, in this case, by means of telemetry.

Referring now to FIG. 4, the MCU 10 is shown connected by the A/V switcher buss 12 to a plurality of A/V switchers 18 which, as shown, may include a plurality of A/V switchers, in this case 6 such A/V switchers 45 through 50, respectively. The A/V switcher buss 12, which is used for control purposes, is daisy-chained as shown at 12a through 12a through 12e to A/V switchers 45 through 50, respectively. Each of the A/V switchers is capable of receiving ten different input signals, one from each of ten sources. Thus, ten signals may appear on buss 51 from ten sources as schematically indicated at 52, and be applied as input signals to A/V switchers 45, 46 and 47 by the daisy-chained connection shown at 51a and 51b. Each of the A/V switchers has twenty A/V outputs as indicated at 53, each of which may be connected to any given remote station. Thus, A/V switcher 45 may have up to 10 input signals connected to twenty remote stations. By adding A/V switchers 46 and 47 as shown, forty more remote stations may receive the ten signals from ten sources. The number of A/V switchers may be expanded as at 51c to provide outputs as desired for the number of stations in the system.

If additional sources are employed so that more than ten inputs are provided, then additional A/V switchers may be added as at 48, 49 and 50 each of which receives 10 signals over the buss 61 from the ten sources 62. The buss 61 is connected as before as shown at 61a and 61b and may be expanded as at 61c. Each of the twenty outputs 63 from A/V switchers 48, 49 and 50 is connected to its corresponding output in A/V switchers 47, 46 and 45 respectively over cables 64, 65 and 66 respectively. Thus, each one of 60 remote stations is now capable of receiving anyone of twenty signals generated by twenty different A/V sources. It should now become clear that additional A/V switchers may be deed as desired for any system to receive signals from any desired number of sources and direct them to any desired number of remote stations.

In general operation, control signals are manually inserted through a keyboard into the individual remote stations to await instructions from the MCU 10 to transmit. The MCU 10 generates a signal which in effect sequentially addresses the stations and instructs an addressed station to transmit its stored information over the station buss 11. The MCU monitors this information and it is transmitted over the source buss 13 to the source terminals. By appropriate comparison of the source address contained in the generated signal with the address of the sources associated with a particular source terminal, control is effected of that source by the generating remote station.

The information which is generated by the station includes a source address and appropriate function commands or the like which are registered in the MCU 10 and thereupon a signal is generated to the appropriate A/V switcher to transfer information from the source to that station. The MCU 10 is a digital data processor and is capable of processing 1,000 remote stations and 1,000 A/V sources so as to generate 1,000,000 switch points (1,000 stations × 1000 sources).

Master Control Unit

Considering the system in greater detail, and with additional reference to FIG. 5, the station buss 11 includes a sheath 71 encasing 6 twisted pair of electrical conducting wires to form a 6 signal conductor cable. The MCU 10 includes an oscillator 72, a program counter 73, a data generator 74, a demodulator 75 and a station and source address register 76. The program counter 73 generates signals to effect generation of other signals by other components to the MCU, of the stations and/or of the source terminals. The data generator 74 generates information identifying and addressing particular stations. The oscillator 72 generates a strobe or clock signal which is utilized to cause each of the stations and/or sources to respond at the same time and at a predetermined period of time such that there is no interference with the program counter and data generator signals. The output from the MCU 10 consists of four signals from the data generator, each signal in binary code decimal format, a strobe signal and a synchronizing signal (which is transmitted once during each cycle of the program counter to synchronize the entire system as is well known in the art). This information is fed as shown, on the six conducting wires of the buss 11-13 to the station terminals and source terminals, and from there to the stations and sources.

Station Identification and Transmittal

The MCU 10 monitors the line to prevent two stations transmitting simultaneously. Identification of a station and command to transmit is accomplished by sequentially addressing each station in accordance with the program as set forth in TABLE I.

TABLE I

Stroke Program DATA or Counter SIGNAL Clock Step (Stations Transmit Cycle) __________________________________________________________________________ 1 0 Mode 1 1 Station Hundreds Digit 1 2 Station Tens Digit MCU 1 3 Station Units Digit Generated 1 4 Station Status 1 5 Command 1 6 Source Hundreds Digit From 1 7 Source Tens Digit Station 1 8 Source Units Digit 1 9 Program Tens Digit 1 10 Program Units Digit 1 11 Function 1 12 Station Hundreds Digit 1 13 Station Tens Digit 1 14 Station Units Digit MCU 1 15 Repeat Generated __________________________________________________________________________

Referring to TABLE I, at each step wherein the program counter and data signals are changed, a strobe signal is generated so as to effect timed response as hereinabove indicated. When the program counter and data signals are both in their zero position a scanning mode is initiated. Thereafter as the program counter steps through its binary code decimals, the stations are sequentially addressed by having the data signals generated in the order shown, that is, first the hundreds digit then the tens digit and then the units digit are generated in binary code decimals. These signals are fed along the station buss 11 to all of the station terminals 14 and a particular remote station is identified. For example, as illustrated in TABLE I, when the program counter step is at 1, then the signal from the data generator identifies the 100's unit of the particular station to be addressed. When the program counter step is at 2, the data signal identifies the 10's unit of the station to be addressed, and in like manner the units digit is identified upon the program counter step being at 3. After the station has thus been identified, that station will be caused to transmit certain of its information, as hereinafter described, and all of the sources will be caused to receive the signal thus transmitted assuming that the station which has been addressed does in fact have information to transmit. This transmission is indicated in TABLE I wherein as the program counter steps through position 4 the status of the station addressed is transmitted by that station, i.e., ACTIVE, MONITOR, ON LINE, FUNCTION or COMMAND CHANGE. When the program counter is at step 5, the desired command is transmitted by the addressed station, i.e., transmit or cancel. When the program counter goes through steps 6, 7 and 8, the addressed station transmits the address of a source it desires to control by transmitting the 100's digit the 10's digit, and the units's digit of that address, respectively. As the program counter goes through its next step a function code is transmitted, i.e., RUN, STOP, FORWARD, REVERSE, if in fact such exists for the particular source being addressed. If the source has no such function, then zeros are transmitted to so indicate. As the program counter goes through steps 12, 13 and 14 the station address is repeated by the MCU for use by the source terminals. At step 15 a command may be received from the computer (if one is connected) to cause the entire sequence of signals to be repeated.

After the foregoing stage of transmission and reception has occurred, the entire process is repeated for the next sequential station, and so on until all 1,000 stations have thus been identified and have had an opportunity to transmit.

Referring now to FIGS. 6, 7 and 8, the manner in which the stations are associated with their terminals 14 and the manner in which they receive and transmit signals are shown. With specific reference to FIG. 6, each station 82 has a keyboard 81 or 81a which feeds information to be transmitted into a register 83. The output of each register is fed onto a common buss 84 for transmittal over a line 85 (see FIG. 7) to the station buss 11. In order to minimize wiring, a "looping" connection system is utilized throughout, wherein drivers 54 and receivers 56 are connected in parallel to the buss 11, and such components are utilized where appropriate, although not specifically illustrated in the drawing.

The output from the register 83 is fed through an appropriate logic element, such as a nand element 86, on signal from the station terminal 25. Thus, the information which is transmitted by the station by manipulation of the keyboard 81 is stored in the register 83 for further transmission. When the MCU applies a particular station address identifying a given station its respective station terminal, an additional output is then transmitted to the nand logic element causing it to transmit the information stored on the particular register of the station which has been identified, onto a common buss 84, into the terminal 25 and from there onto the station buss 11 via the connecting line 85.

Referring specifically to FIG. 7, the station address generated as a data signal (TABLE I) is applied through a demodulator 91 to a station address comparator 92 in each of the station terminals. If the hundreds and tens units of the station address is transmitted compares with the hundreds and tens units of the stations associated with the terminal, then the units code as transmitted is applied to the eight transmission lines shown at 93. Each of the stations which are operatively associated with the station terminal 25 are each individually connected to four of the eight lines 93 in binary code fashion so that only that station which is addressed by the units code will respond.

The manner of such connection is illustrated in FIG. 8 wherein it is seen that each of the lines represents an "0" or a "1" binary code decimal. The unit's signal is applied to the lines in accordance with its binary code decimal equivalent so as to generate a logically true signal over four of the lines. That station which receives a logically true signal over each of its four connecting lines is the station being addressed by the signal.

Remote Control Station

As described above, in response to being addressed, as the program counter steps through its next eight positions the station transmits a signal in binary code fashion of the device it wishes to control along with a function and program signal. Referring to FIG. 9, each remote control station 82 is equipped with a 12 button telephone-style keyboard 81 which allows the operator to address any of the source and control functions available in the system. A variety of capabilities can be provided ranging from simple numeric selection of a source to detailed control of a source and of a sequential tape search mode. The particular remote control station 82 depicted in FIG. 9 provides for the numeric selection and subsequent operator control of one of a possible 1,000 A/V sources and can enter tape search data to digitally locate particular tape recorded programs.

In particular, five illuminable control status indicator switches 101-105 are provided and labeled, respectively, "active", "stop", "fast forward", "reverse" and "show". The control status is displayed upon selecting a source. If control is available, an "active" indicator lights up indicating that control has been automatically delegated to the station. Should the station be assigned a monitor mode as a result of some other station being in control, the "active" indicator 101 will not be illuminated, but rather a "monitor" indicator 106 will be illuminated. Upon the relinquishment of control by such other station, the "monitor" indicator light 106 will blink. The first station to have its "transmit" switch depressed will establish control and that "active" light will become illuminated while the other viewing stations will have their "monitor" indicators illuminated. Control may also be assigned to a station or taken away by a supervisory control station in the system as hereinafter described and will be displayed accordingly by the "active" or "monitor" indicator lights.

The "stop", "forward", "reverse" and "show" switches 102-105 are utilized for a search mode operation on an audio or video recorder as contro-led by a tape search and source controller such as that indicated at 70 in FIG. 10. During the search mode the forward or reverse indicator lights are on to indicate the direction of search. At the completion of the search sequence, the source goes into a play mode and the "show" indicator 105 is illuminated. The "monitor" indicator 106 is illuminated when the selected source is not available for search; however, an A/V switch is accomplished via the A/V switcher to place the station in a monitor mode.

Source Control

Referring to FIG. 10, each of the devices or sources of information, such as a tape recorder 111, motion picture film projector 112, 35 mm slide projector 113, or other audio and/or visual device, is connected to an individual controller for that source. The control may include tape search and programming functionings as illustrated by the tape search and source controller 70 or may be of simpler construction for utilization with unprogrammed devices such as the ones illustrated by the source controllers 114, 115 and 116. Each source controller 70, 114, 115 or 116 accepts control commands from a source terminal 35 which is common to a plurality of the source controllers, as illustrated in FIG. 8.

Referring to FIG. 11, the source address generated as a data signal (TABLE I) is applied through a demodulator 121 to a source address comparator 122 in each of the source terminals such as 35. If the source address as transmitted compares insofar as the 100s and 10 s units with the 100 s and 10 s units of the sources associated with that terminal, then the units code as transmitted is decoded through the demodulator 121 and applied to the eight transmission lines shown at 123. Each of the sources which are operatively associated with the terminal 16 via its source controller are each individually connected to four of the transmission lines 123 in binary code fashion, in the same manner as described with respect to the connection of the stations to the transmission lines 93 of the station terminal 25, as illustrated in FIG. 7. The particular source which is addressed and only that source will respond. In the event that that particular source is not at the moment being controlled, it will provide a signal to indicate its lack of control. This can be accomplished by a flip-flop circuit at the source controller having a "1" and "0" state. If the flip-flop is in the "0" state, this indicates that the source being addressed is not being controlled and is free to be controlled by the addressing station. If the flip-flop is in the "1" condition, and the station "active" indicator is on, then the function is transferred over the line 127 to a relay interface 128 at the source controller for utilization with the particular device being used as the source. In the event that the source controller and the source associated therewith are such that a search mode would be required or desirable for that particular source, then the program address relating to the searching concept would be similarly transferred. In the event that the source controller indicates that it is uncontrolled, i.e., the flip-flop is in the "0" condition, then when the comparator enable signal is generated, the address of the station which is stored in the register 124 at the terminal is transferred over the line 126 to the source controller station register 127.

In the source being utilized, such as a tape recorder, a television tuner, a camera or the like, a signal is developed in response to a particular function control such as forward, reverse, stop, show, or the like. In the event that a particular function has been ordered, a signal can be developed by the device going into that mode of operation which can be transmitted back to the stations. Thus, the station address as contained in the register 124 at the source controller and the status information contained thereat in the status register 129 are transmitted via the lines 131 and 132, respectively, and 133 along the buss 11-13 to the stations in the manner as will be indicated hereinafter with respect to scanning operation. A signal is thereby activated at the station that the particular source equipment is in the desired mode of operation, thus providing a check for the operator of that station that the source has responded properly to the function as commanded by the station operator. If such a closed loop is not desired in a particular system, this feature of retransmittal of the command can be eliminated.

If the flip-flop is in the "1" condition and the station "monitor" indicator is lighted thereby indicating control by a different station, no further action by the source controller takes place with regard to the information in the source terminal registers 123 and 124.

Device Scanning

It is desirable to indicate to each of the stations the status of a particular device at any given point in time so as to signal to the controlling station and the monitoring station or stations a change in status of the device or source. A signal from the master control unit 10 is utilized for scanning the devices at a point in time when the master control unit 10 has stepped through all the stations. As that point, the master control unit will generate signals as set forth in TABLE 2.

TABLE

2 Strobe Program DATA Counter SIGNAL Step (Sources Transmit Cycles) __________________________________________________________________________ 1 0 Mode 1 1 Source Hundreds Digit 1 2 Source Tens Digit 1 3 Source Units Digit 1 4 -- -- -- 1 5 -- -- -- MCU 1 6 Source Hundreds Digit generated 1 7 Source Tens Digit 1 8 Source Units Digit 1 9 Program Tens Digit 1 10 Program Units Digit Source 1 11 Source Status generated 1 12 Station Hundreds Digit 1 13 Station Tens Digit 1 14 Station Units Digit Source -- 15 -- -- -- __________________________________________________________________________

Referring to TABLE 2, the first data signal generated in this scan mode is an invalid number such as 1111 to indicate that the mode is in fact a scan mode. Subsequently, the hundreds, tens and units in binary code decimals of the source address is generated by the MCU 10 as was done with respect to the stations address as previously described in conjunction with TABLE I. When this occurs, and referring to FIG. 7, the device address is stored in a register 141 at the station terminal 25 and applied to the comparator 92 at the station terminal in a manner similar to that previously described with respect to station scan.

The addressed source is caused to transmit. During the program steps 6, 7 and 8 the MCU retransmits the source address transmitted during steps 1, 2 and 3. This source address is compared to the stored source address at every remote station. Upon coincidence between stored and transmitted source addresses a source match flip-flop is set at the remote station. At the step 11 program counter the status of the source which has been addressed is transmitted. The source match flip-flop being in a true state causes the source status data to be transferred to that particular station, thus causing a given indicator to light up at that station indicating the status of the device. For example, and referring to FIG. 9, an appropriate indicating lamp such as the "stop" 102, "forward" 103, "reverse" 104, or "show" 105 lamp will be illuminated as determined by the status signal to indicate the status of the particular source.

During the steps 12, 13 and 14 of the program counter the source which is addressed is permitted to transmit the address of the station which is controlling it. As the address of the controlling station compares to the address of a particular station, then a signal is generated which lights an appropriate indicator at the station. In this particular system, and referring again to FIG. 9, such an indicator is the lamp 101 marked "active". In the event that the station addresses do not compare while the source addresses do compare, the "active" lamp 101 will not be illuminated, but another appropriate indicating lamp 106 indicating "monitor" will be illuminated along with the particular function lamp 102-105 as above, to indicate that the source is not available for control by this particular station, but that the station can monitor a signal from the source and hear and/or view it if such is desired.

Change of Control

Referring now to the situation which occurs when a station relinquishes control or monitoring of a particular source. If the station is merely a monitoring station and is non-controlling nothing will change in that particular source or source controller. The message of termination being transmitted by that station will be received by the source controller in the manner previously described. The station address contained in that message of termination will be compared to the station address in the source controller register 127 (FIG. 12) and, since the addresses will be different, no further action by the source controller will take place. However, the MCU 10 will signal the appropriate video switcher to terminate transmission of information from the source previously monitored. On the other hand, if the station transmitting the termination message has a station address which compares with that stored in the source controller register 127, the following sequence of events will occur. First of all, the function of the source 150 will not change since other stations may be viewing the source although they are not controlling. However, the flip-flop is reset from its one to its "0" state. This resetting causes the station address appearing in the source controller shift register 127 to be automatically set to an invalid number, that is, a number which cannot actually occur through utilization of the digits 0 through 9. The entire signal now stored in the source controller serial shift register including the invalid station address, is transmitted back to all of the stations. At each station a comparison is made as before so that if the source address is the same as registered at that station, then a lamp is activated which indicates the particular function contained in the transmitted message. However, as noted above, another comparison is made with the stored station address. Since the station address transmitted with the message is now invalid, it will indicate a non-coincidence with the station addressed stored in each of the stations. In the previous description herein such non-coincidence was indicated by the illumination of a "monitor" lamp 106. However, in this particular instance, a further comparison is made wherein it will be indicated that the station address contained in the transmitted message is composed of an invalid number, e.g., entirely of ones. When this occurs, the "monitor" lamp 106 will blink. This provides information to the operators of the stations which have been non-controlling, that if that station wishes to gain control of this particular source, all that is required is that the "transmit" button 100 be pushed. This will in turn cause the transmission of a signal from that station to all of the source controllers, as described above. Accordingly, the sequence of events as above described will occur with the station having its "transmit" button 100 first pushed and that station address will be transmitted to the source controller register 127 and the flip-flop transferred from the "0" to the "1" state, thus causing that particular station to now have control.

Supervisor Control Station

Referring to FIG. 13, a supervisor control station 160 is illustrated. This station can be utilized simply as a monitor station or as a remote control station similar to that indicated at 82, it can select to display a station status, a source status, or it can be utilized to override the control by any station in the system, or can delegate control to any station in the system. The supervisor control station 160 also has a telephone-style keyboard 81a whereby it can serially enter an eight digit number. When utilized in a monitor mode only, the first three digits are the address of the supervisor control station, the next three digits are the desired source address and the last two digits are the desired program number at the source (if the source is not equipped with a search unit, only a six digit number is entered). After data are entered a transmit button 161 is depressed to send the data to the MCU 10 over the station buss 11. A "cancel" button 162 is provided which upon depression thereof takes the supervisor control station 160 "off-line" or corrects a data entry. An eight digit nixie display 163 is provided to indicate the address of the remote station, the source and the program as appropriate.

In the delegation mode, an eight digit number is also entered onto the keyboard. The first three digits are the address of a remote station selected for delegation. The next three digits are the address of the desired source. The last two digits are the desired program number at the source if the source is equipped with a search unit. After data are entered, the "transmit" button 161 is depressed to send the data to the MCU 10 to thus route the source data to the addressed remote station. This operation may be repeated until all desired station/source connections are made. To delegate source control to a station an "active" button 164 rather than the "transmit" button 161 is depressed after data are entered. Status indicators 165-168, corresponding to those of the stations, provide a display of whichever station the supervisor control station is addressing. To accomplish the delegation mode, the supervisor control station transmission message contains an appropriate signal which is received by all of the stations, but acted upon only by that station having a station address identical to the station address as transmitted by the supervisor control station. The addressed station acts upon the information to replace the source address in its register 83 (FIG. 6) with the source address contained in the transmitted message from the supervisor control station.

In the override mode, again an eight digit number is entered. The first three digits are the address of the supervisor control station 160. The next three digits are the desired source address. The last two digits are the desired program number at the source, if equipped with a search unit. After the data are entered, the "active" push button 164 is depressed causing the supervisor control station to obtain control of the source as well as to remove control from whichever station previously had control. However, all stations previously receiving information from the source remain in a monitor mode. The "active" indicator 164 at the supervisor control station 160 will be illuminated as well as whichever indicator corresponds to the current status of the source; the function control push buttons 165-168 are activated to allow the supervisor control station 160 to control the source. The message transmitted by the supervising control station is received in the source controller station address register 127 and the status register 129. If a function mode is contained in the message, it will totally override the station address appearing in the source controller register 127 and cause control to be assumed in accordance with the function code appearing in the message from the supervisor control station 160. When this occurs, the station addressed by the supervisor control station 160 assumes control irrespective of the address of the station appearing previously in the register 127. The supervisor control station can obtain such control by transmitting his own address as an overriding station address.

An additional feature of this system, in the event that the station controlling the source has commanded the source to a status different from that which it presently occupies, the source will transmit back its present status and then as soon as the status of the source has changed to that commanded, an additional signal indicating the new status is transmitted back to all of the stations. During the interim while the source is changing from its current status to the commanded status, the lines are open for additional utilization by any other station to any other source. Such time sharing utilization may be effected for any function of the source which requires several seconds at a time such as searching or the like. To effectuate such time sharing, the present and changes status signals are transmitted together with the device address and station address to be received by the stations in the manner indicated above.

Audio-Video Switcher

Referring to the function of the A/V switcher, and referring back to FIG. 4 and to the description of the MCU 10 particularly with respect to its register 76, that register 76 is adapted to receive only the source address and the station address. When the 100s, 10s and units numbers of these two addresses are stored therein, the register 76 is not capable of receiving any further information and a load pulse is generated which is applied to an A/V switch interface which indicates to receiving apparatus that the video switch can now be activated to accomplish the interconnection of the particular source whose address is in the register 76 to the particular station whose address is stored therein. The aforenoted load pulse may be generated by a variety of methods. In a particular method, the MCU 10 is adapted such that when the bits of information containing the station address and device address have been received by the register 76, a counter therein (not shown) indicates this by moving through separate increments. At this point, a signal is generated which causes the register 76 to not receive additional information and simultaneously also causes a load pulse to be generated by equipment therefor (not shown). The structure of the components are such that after the station has utilized information, or if the information has not been utilized in a predetermined period of time, a signal is generated by the station so as to cause the switch to be deactivated insofar as that device-station interface is concerned.

As indicated in FIG. 4, the signals from each of the ten sources are connected through an appropriate decoder to a common buss which would be connected to an amplifier the output of which is one of the twenty outputs. The station and source address signals then are used to interconnect cross points thereby to apply the desired input signal to the desired amplifier.