Title:
Radio telephone system
United States Patent 2265056


Abstract:
This invention relates to radio systems, and particularly to radio telephone systems adatped for communication between ships and points fasorec In such systems, it is frequently the practice to only transmit the carrier wave in a given direction when talking in that direction the socalled "cut...



Inventors:
Franklin, Bowers Albert
Application Number:
US35862140A
Publication Date:
12/02/1941
Filing Date:
09/27/1940
Assignee:
AMERICAN TELEPHONE & TELEGRAPH
Primary Class:
Other Classes:
455/403
International Classes:
H04W84/02; H04W84/04
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Description:

This invention relates to radio systems, and particularly to radio telephone systems adatped for communication between ships and points fasorec In such systems, it is frequently the practice to only transmit the carrier wave in a given direction when talking in that direction the socalled "cut carrier" method of operation. This method of operation permits the use of a relatively simple scheme for signaling the shore station. If, in such a system, the ship operator desires to call the shorestation (or stations, where more than one shore station is provided), he may do so, simply by causing the carrier to be sent from ship to shore. The carrier, when received by the shore station, causes a lamp pr other signal to be actuated at the technical operator's position and at the shore traffic operator's position, sometimes referred to as the marine operator's position. In a system operating accordin to this plan, each time the ship subscriber talks the transmission of the carrier necessary for this purpose would result in reactuating the signal. The circuit is therefore so arranged that when the marine operator ashore 2 answers the call, the signallamp or other signaling device will be rendered inoperative so it does not respond to future transmissions of the carrier as long as the connection remains established during the establishment of the onnection.

This method of signaling has involved the diffculty in practice that false operation of the signal lamps at the positions of the marine operator and technical operator occurs in response to interfering frequencies which happen to fall within the band accepted by the shore receivers' range of the communication system. To s e extent this difficulty may be reduced by narrowing the band to which the signal-actuating apparatus is responsive. But even so, false operation of the signal frequently occurs, due to interfering stations sending out harmonics which happen to fall within the narrow band through which is passed the carrier of the system in question. This false operation of the signal at the marine operator's position causes theoperator to plug in frequently to answer calls that are nonexistent, thus increasing the amount of work stet, the us ireasg the amod In accordance with the present invention it is proposed to overcome this difficulty b providing tie subescriber at the ship station with a codeseni sg device such as a dial, so that whe snd his cazrier to the shore station he may 05 interrupt it inaccordance with a code. At the shore station, equipment including a selective switch is then provided so that the marine Pperator's signal will only respond to successions of carrier spurts corresponding to the code. Continuous interference or occasional spurts of interfering current will therefore be less apt to cause false operation of the signal. The dial need only be used at the beginning of the call because the operator extingu.ishes the signal as soon as she plugs in to answer the call.

ince a selective switch is provided at the shore station to operate the signal in response to dialing, different pcodes may be used to operate other signals in addition to the one to the marine operator. For example another code may be used to signal -the technical operator, if desired. In addition there are several special signals such as distress calls, urgent calls and calls indicating dangers toanayigation that may be made by merely dialing other suitable codes to operate special lamps or other signals indicating such special calls.

The invention may now be more fully understood from the following description, when read in connection with the drawing, in which a schematic layout of a ship-to-shore radio telephone system embodying the invention is llustrated.

In the drawing, the marine operator's position ashore is shown at A and the apparatus -at the technical operator's position is illustrated at B.

The shore radio transmitting and receiving equipment is usually at esome distance from the operators' positions and is illustrated at C. The equipentaboard ship is indicated schematically at D.

The appratus at station D includes:a radio reeiver BR, normally conditioned to receive, and a radio transmitter aBT which is normallyinoperative. As the radio receiver and radio transitter are well known types of apparatus, they are schematically represented inthe diagram as simple boes. A handset HS is also-prvided, the receiver t1 of the landset being connected through a transformer to the.outppt of the radio receiver BR. Likewise the transmitter T of the handset is connected through a transformer to the input of the radio transmitter BT. An oscillator 0 is associated with the radio transmitter BT and forms a part thereof. The purpose of the oscillator is to supply the .carrier frequency and it is normally disabled so that the carrier frequency is only sent out when the radio transmitter is he used in talking from ship to shore.

A push button K is provided pn the handst, and a relay SR, controlled by the push button exercises control over the circuits of the radic receiver, radio transmitter and oscillator b3 means of its contacts. Normally the relay SR ih deenergized and the circuit of the radio receivei is rendered operative at the upper back contact of the relay. When, however, it is desired to call the operator or speak into the transmitter T, the push button K is operated to energize the relay SR, which at its upper contact opens the circuit of the radio receiver and thereby disables it, while at the same time the lower front contact of the relay SR closes the circuit of the radio transmitter BT. Likewise the middle front contact of the relay SR closes the circuit of the oscillator 0 so that the carrier current is now supplied to the radio transmitter. By merely manipulating the key K the talker can disable the radio receiver and render the radio transmitter operative while he talks, and upon releasing the key the condition is reversed so that the radio transmitter is disabled and the receiver is placed in operative condition to receive talk coming from the shore station.

As will appear later, this switching operation, with its consequent control of the carrier, is used at the shore station to alternately permit transmission to and from the radio transmitter and radio receiver respectively. This control is effected in such a way that the radio receiver ashore is normally conditioned to receive and the path to the transmitter is disabled. When no carrier is being sent out by the ship station the operator ashore may, by plugging in, condition the transmitter so that the ship may be signaled. If the land station is not calling, however, the receiver ashore will receive the carrier sent out from the ship when its operator actuates the key K to call. After the call has been answered by the shore operator and the carrier sent out from the ship ceases, the normal condition is reversed and the radio transmitter ashore is put in operative condition and the receiver disabled. Thus it is evident that the switching operation between radio transmitter and radio receiver, both aboard ship and on shore, is under the direct control of the key K on shipboard.

The radio transmitting and receiving apparatus ashore is indicated schematically at C. The system illustrated by way of example is a telephone system adapted for communication with ships operating within a limited area such as a harbor, and includes a single radio transmitter ST, which may be of any known type and is illustrated as a simple box. A voice frequency amplifier AT is associated with the radio transmitter ST. This equipment is connected by means of a wire line TL to switching, signaling and controlling apparatus at the marine operator's po- G sition A and the technical operator's position B.

Although the ship moves about so that it is in different positions both as to direction and distance with respect to the radio transmitter ashore, it has been found that a single trans- o mitter, located at a fixed position, is sufficient for transmission from the shore to a ship at any reasonable location.

Since it is not always possible to use a high power transmitter on board ship, it is desirable to 7( have several receiving stations located at different convenient points along the shore, so that in transmitting from ship to shore the nearest convenient shore receiving station can be used. Consequently at C two radio receivers, SRi and 7 SR2, are schematically shown. These receivers Sare of a known type and are therefore illustrated by block diagrams. It will be understood, of s course, that more than two radio receivers may * be provided if desired. These receivers SRi and S SR2 are connected by means of lines RLi and I RL2, respectively, with the apparatus at the technical operator's position.

Each radio receiver ashore is provided with a codan (shown schematically at CODI and COD2.

The codan is of a known type and is therefore shown as a simple block. It receives its name from the fact that it is a carrier operated device which is as unresponsive as possible to noise, the I name codan being formed from the initial letters of the phrase "carrier operated device antinoise." The normal function of the codan is to insert a high loss in the output of the radio receiver with which it is associated when no carrier signal is being received. As this is a function with which the present invention is not concerned, such controlling apparatus, which is well known in the art, is not illustrated.

Each codan is provided with a so-called codan relay illustrated at CRi in the case of receiver SRi, and at CR2 in the case of receiver SR2.

The codan relay may have two windings, one of these windings being responsive to a rectified current resulting from the selected carrier, and SO the other being responsive to a rectified current resulting from noise. The circuit of the codan which controls the carrier responsive winding may be made sharply selective to the carrier while circuit controlling the noise responsive winding is made receptive to all frequencies within the side-band range except in the immediate vicinity of the carrier. The result is that the codan relay has its armature thrown in one direction by means of the rectified noise currents when no carrier is being received. When, however, the carrier current comes in and is rectified, the rectified current in the carrier responsive winding of the codan relay causes the latter winding to predominate in its effect over the other winding and swing the armature of the relay to the opposite position. As shown, when the codan relay pulls up in response to the reception of carrier, its armature connects ground to a simplex circuit extending over the line RL or RL2 as the case may be, connecting the radio receiver to the technical operator's position.

The current thus transmitted over the simplex circuit is used at the technical operator's position to perform various functions, including the actuation of a signal at the technical operator's position. Also it has been the practice, prior to the present invention, to use this current to actuate the signal lamp at the marine operator's position A. In accordance with the present in;0 vention, however, a relay ISi is included in the simplex circuit operated by the codan relay which establishes an auxiliary circuit (Xi in the case of radio receiver SRi) leading to the technical operator's position, where the circuit may 5 be used to effect the setting of a switch under the control of the dial aboard ship, as will be described later.

An example of apparatus for switching, signaling and otherwise controlling the transmission 0 circuits is located at A and B-principally at the latter position. A common transmission path or line L may be provided and this may be switched to a transmitting line TL leading to the radio transmitter ST or to a receiving path RL leading to a receiving amplifier RA, the input of which is branched to each of several lins RIl, BlS e etc., leading to individual radio receivers such as SRi and SR2. The line L may be optionally switched to the transmission path TL or the receiving path RL under the control of a polar relay. SW, which is under the control of the push button K at the ship station D. The transmitting path TL may also include a so-called vogad for automatically adjusting the gain of the transmission path in a manner well known in the art, its name being derived by using -the initials of the expression "voice operated gain adjusting device." This device is well known and, as it is not concerned with the present invention, is illustrated by a conventional box or rectangle.

As already stated, the input of the receiving amplified RA in the receiving path RL may be branched to several transmission paths leading to individual radio receivers. Each of these paths may include an equalizer and pad network 21 of well known type, illustrated at REi and RE2.

The present invention is not concerned with the details of these pieces of equipment and, as they are well known, they are merely represented symbolically. 2 A polar relay Ci is associated with the path RL and a similar relay C2 is associated with the path RL2. Each of these relays has a lower biasing winding. The upper winding in each case is connected to the simplex circuit previously de- 3 scribed as controlled by the codan relays ;CRi and CR2. The middle winding is connected to another simplex circuit with which we are not here concerned, so that it has not been illustrated. For purposes of the present invention it is sufficient to know that when the codan relay CRi, for example, connects ground to the simplex circuit associated with the upper winding of the polar relay Ci, the armature of said relay will be shifted from its back contact to its front contact to produce certain effects which will be desribed in more detail later.

One of these effects is to cause the operation of the technical operator's lamp TOL when the carrier (or interference) causes the operation of the codan relay. In systems of the prior art the actuation of the relay Ci also energized the signal lamp at the marine operator's position to apprise the :operator that an incoming call was being made from the ship at D. Since, however, the codan sometimes operated in response to interference, false signals would be received by the marine operator and to avoid this the marine operator's call lamp MOLi and MOL2 are actuated by a dial-controlled switching arrangement about to be described. hether the lamp MOLi or the lamp MOL2 is to be used depends upon which one of the receivers SRi or SR2 is close enough to the ship at D to receive its signal While any suitable dial-controlled switch may be utilized, the switch herein illustrated is of the up-and-around type frequently used in step-bystep automatic switching systems. The switches which control the lamps MOLi and MOL2, respectively, are separately controlled through the radio receivers SRi and SR2. As they are identical, however, only one need be described. Th switch which is controlled from the receivin radio receiver SRi, for example, comprises . wiper W :shown at position B, which, under th control of a vertical stepping magnet "V, man be stepped vertically to the level of any one o ten banks of contacts, each having ten con tacts in each bank. This action is taken b the switch in response to the first digit sen by the dial SD at the ship station D. In response to the second digit dialed, the wiper W2 will be rotated step-by-step by the rotary magnet Ri to a particular contact in the vertical row or level to which the wiper has been previously elevated.

s shown if the number 50 is dialed, the first five impulses will elevate the wiper Wi to the fifth row of contacts, and the succeeding ten impulses will rotate the wiper to the tenth contact in that row to complete the circuit of the marine operator's lamp MrOLi, thereby indicating that a call has come in. When the train of carrier waves sent out from the ship comes to an end the release magnet Yi restores the switch to normal in a-well-known manner. The stepping of the switch is controlled by relay ITI, connected to an auxiliary circuit Xi leading to the distant radio receiver SRi and operated by the relay IS1 under 0 the control of the codan relay CRi. A similar relay ITs, controlling the switch associated with the path La, is operated over an auxiliary circuit Xa from the radio receiver SR2.

The marine operator is provided with jacks Ji and J2 for completing the connection in the case of a call signal received from either of the radio receivers illustrated, it being understood that any desired number of radio receivers may be employed, in which case there will be an additional 0 jack for each additional receiver. If the dial signal is received by the radio receiver SRi so that the marine operator's lamp MOLi is actuated, the marine operator will plug in to the jack Ji. If, on the other hand, the signal is received from the 5 radio receiver SRa, the operator will go in on the jack J2.

As soon as the operator plugs in, the sleeve relay Si is operated to disable the signal lamp.

The relay Si may also be provided with an extra 40 contact to open the circuit by which relay ITi, operates relay LRi, thus preventing operation of the switch during .conversation. Relay Si also actuates a secondary relay 82. The latter in conjunction with the polar relay Ci controls 45 certain switching operations which will be more fully described later. By one of these switching operations the common receiving circuit RL is extended to the receiving branch path circuit leading to the radio receiver which is receiving 50 the signal from the ship. Another of these switching operations, which is ultimately controlled by the push button K at the ship station, is the switching of the common path L between the transmitting path TL and the receiving path 55 RL. The relay RECi completes the .connection from the common receiving path RL to the individual receiving path RLi, and the corresponding relay associated with the receiving path RLI will (in case the signal is being received from 60 the radio receiver SRi) connect the common receiving path RL to the individual receiving path RL2.

Further details of the system will be better apprehended from a description of the operation, 65 which is as follows: Let us suppose that the ship at D is located e nearer to the radio receiver SRi than to the S radio receiver SR2. In the normal condition of a the circuit the polar relay SW is actuated only e 70 by its upper or balancing winding and holds its S armature in such a position as to close the conf nection from the common path L to the common receiving path RL, the transmitting path TL y being disconnected from the common path L, t 75 At the ship station, in the normal condition of the circuit, the push button K is not actuate and consequently the relay SR is deenergize( so that the radio receiver BR is in receiving con dition. When this condition obtains, the radi transmitter BT is disabled.

If, now, some one aboard ship desires to tele phone, he presses the push button K and oper ates the dial SD to dial the combination whicl will operate the marine operator's line lamp In the instance illustrated, this will be accom plished by dialing 50. As soon as the push but. ton is operated the relay SR is energized to oper the circuit of the radio receiver BR and close the circuit of the radio transmitter BT. At the same time it also closes the circuit of the oscillator O to supply the carrier to the radio transmitter. The carrier, upon being transmitted, will be received by the radio receiver SRi and will operate the codan relay CRI, which in turn completes a circuit through the relay ISi over the lower side of the path RLi to the upper winding of the polar relay C1. This causes the polar relay Ci to shift its armature to its lower contact. This completes a circuit for the relay FL from battery through said relay over the lower back contact of the relay REC1, front contact of polar relay C1, upper back contact of relay REC1, and back contact of relay SCO to ground.

Relay FL opens the circuit of normally energized slow release relay T, which completes a circuit through the upper winding of the relay INC.

Relay INC completes the circuit for the lamp TOL at the technical operator's position.

In circuits employed prior to the present invention the connection above described was extended also to the marine operator's lamp MOLi.

With the circuit wired in accordance with the present invention, any condition that operates the codan relay CRI will operate the lamp TOL at the technical operator's position, whether it be the ship calling or an interfering condition, but the marine operator's lamp MOL1 will not be operated.

In accordance with the present invention, it is necessary for the caller at D to do something more than merely press the key K in order to call the marine operator at A. After depressing the key K the caller must next operate the dial SD to interrupt the carrier in accordance with a code. In the present instance it will be assumed that the code dialed is 50. This will first interrupt the carrier five times. The fifth interruption is followed by a spurt of carrier, and then the carrier is interrupted ten times in succession. It will be noted that when the carrier 5 is sent out by depressing the key K, the codan relay CRi operates the relay ISi. This in turn completes a circuit from ground over the front contact of said relay and over the conductor Xi (which may be a simplex circuit derived from a 6( spare pair), and through the winding of the relay IT1 to battery. Relay ITi completes a circuit for the pulsing relay LRi, which at its front contact completes a circuit for the slow release relay Di, which will be held up during interrup- 65 tions of the carrier due to dialing. A circuit is prepared for the vertical magnet Vi over the front contact of the slow release relay D1, but this circuit is not completed so long as the carrier remains uninterrupted. 70 When the dial SD is operated, the first interruption of the carrier causes a momentary release of the relay ISi at C, with the consequent release of the relay ITi at B. The armature of the pulsing relay LRi falls off and completes a 75 d circuit over its back contact from ground, over , the front contact of slow release relay Di, over , the normal left-hand contact of the off-normal o switch ON, through slow release relay Di' and through the vertical relay Vi to battery. The pulse through the vertical magnet Vi lifts the S wiper W one step, bringing it on a level with 1 the first row of contacts. At the end of the im. pulse the armature of the pulsing relay LRi is - 10 again drawn up and is followed by the second interruption of the carrier, which again causes the S armature of relay LRi to fall back and complete a circuit from ground over the back contact of said relay, over the front contact of the relay Di and over the left-hand alternate contact of the off-normal switch (ON), and thence over the front contact of slow release relay Di', through the winding of relay Di' and through the vertical magnet Vi to battery. This second pulse through the vertical relay elevates the wiper W1 another step. It will be noted that the pulsing circuit for the vertical magnet Vi is now completed over the front contact of the slow release relay D', which remains energized during pulsing interruptions of the carrier. Successive interruptions of the carrier in dialing the digit 5 send additional pulses over the back contact of the pulsing relay LRi and through the vertical magnet Vi, over the circuit just described, thus stepping the wiper Wi to the fifth row of contacts of the switch.

At the end of the fifth interruption the carrier is transmitted for a longer time than during the periods between dialing impulses and this permits the slow release relay Di' to fall off so that its armature is on its back contact. When the caller at station D dials the first interruption of the ten impulses representing zero, the first interruption causes the pulsing relay LRi to fall 4 off as before. This time it completes a circuit from ground, over the front contact of the slow release relay Di, over the left hand alternate contact of the off-normal switch ON, over the back contact of the slow release relay Di', 1i through the slow release relay Di" and through the rotary magnet Ri to battery. The slow release relay Di" opens the circuit from battery to the wiper Wi during the rotary stepping operation and holds it open until the end of the 0 series of interruptions due to dialing. This first impulse through the rotary magnet Ri steps the wiper W1 horizontal to the first contact in the fifth row, and successive interruptions of the carrier, due to dialing, successively advance this 5 wiper horizontally until it rests upon the last contact of the fifth row.

At the end of the dialing operation the slow release relay Di" falls off and a circuit is completed from battery over the back contact of said relay, over the wiper Wi and the tenth contact in the fifth row, and over the back contact of the relay Si to the lamp MOLi, causing the lamp to glow to apprise the marine operator that a call has come in. If desired another lamp, located at the technical operator's position, may be used in parallel with the lamp MOLi beyond the left-hand armature of relay Si, so that the technical operator's position will be signalled also by this dialing operation. It will be noted that the slow release relay Di is maintained energized from the time the carrier is applied at station D through all of the momentary interruptions due to dialing, until such time as the carrier is interrupted by releasing the key K.

As soon as the marine operator notes that the lamp MOL1 is glowing, she knows that a call has come in through the radio receiver SRi. Of course, had the call come in through the radio receiver station SR2, the dialing operation would have actuated the wiper W2 associated with the circuit L2 and would have caused the lamp MOL2 to glow, which would have indicated a call from the radio receiver SR2. The operator now plugs into the jack Ji, thus operating the relay Si over the sleeve circuit. At its left-hand armature the .11 relay Si opens the circuit of the signal lamp MOLi and at its right-hand front contact it completes a circuit through the relay S2.

Relay S2 at its upper front contact completes a circuit from ground through the winding of 1 relay RECi which at its upper contact extends the circuit RL to the branch circuit RLi leading to the output of radio receiver SR1. At its middle contact relay RECi shifts the ground connection for the armature of the polar relay C 2 from the back contact of the relay SCO to the front contact of the middle armature of relay RECi. At its lower front contact relay REC1 opens the circuit of relay FL which, acting through relays T and INC, opens the circuit of . the lamp TOL at the technical operator's position. The lower armature of the relay RECi at its front contact completes the circuit from ground over its middle front contact, over the front contact of the polar relay Ci (carrier now being received so that this relay is actuated), over the lower front contact of relay RECi, and through the winding of relay SCO, which latter relay is operated.

This condition obtains so long as the push button K is actuated by the caller at station D.

Consequently, from the time the operator answers the call at jack Ji until the push button is released the relay RECi maintains a connection from the common receiving circuit RL, over the upper front contact of the relay REC1, to the receiving circuit RLi connected to the radio receiver SRi at station C. The relay corresponding to RECi, associated with the receiving circuit RL2 is not actuated, and consequently the latter circuit is not connected to the common receiving circuit RL. It will also be noted that the circuit through the lower winding of the polar relay SW is held open by the polar relay Ci because its armature is on its front contact so long as the carrier persists.

Consequently, the radio receiver SR1 is during this period connected over the receiving circuit RLi through the equalizer pad REi over the upper front contact of the relay REC1, through the receiving amplifier RA, over the common receiving circuit RL, and over the lower or front contact of the polar relay SW, and thence over the common circuit L to the branch Li of said circuit leading to the jack Ji, The operator is now able to hear anything said by the caller at station D.

In order that the caller at station D may know that the operator is asking him for information as to the connection desired, he mist, as soon as he has dialed the operator, release the push button K, thus disabling his transmitter BT and putting his radio receiver BR in operating position. This is done through the release of thE relay SR. The consequent interruption of tht carrier at the radio transmitter BT causes th( codan relay CRi to fall off and release the relal IS at C and open the circuit through the uppei winding of the polar relay Ci at B. Polar rela, Ci now shifts its armature' to its upper bad contact and thereby completes a circuit from ground over the middle front contact of relay RECi, over the upper contact of the polar relay' C1, over the lower contact of relay S2, and through the lower winding of the polar relay SW to battery. This shifts the armature of the polar relay from its lower contact to its upper contact, thereby opening the receiver connection through RL and completing the connection 0 from the jack Ji, over the circuit Li, common circuit L, and over the transmitting circuit TL to the radio transmitter ST. The operator is now able to talk. to the caller at D from the radio transmitter ST through the radio receiver BR. The release of the relay ISi, just referred to, and which resulted from the release of the key K at D, disconnects ground from the circuit Xi and thereby causes the release of the relay ITi.

This in turn releases the pulsing relay LR1, ;0 whose armature is restored to its back contact, and as soon as the slow release relay Di releases, a circuit is completed from ground over the back contact of the pulsing relay LRi, over the back contact of the relay Di, over the right-hand con>5 tact of the off-normal switch ON, through the release magnet Yi to battery. The release magnet now restores the switch wiper Wi to normal so that switching apparatus is now ready to respond to a new dialing operation.

30 The caller at D, having heard the operator challenge his call, now pushes the button K, with the result that the relay SR disables his radio receiver BR and applies carrier to his radio transmitter. This operates the codan relay CRi, 35 and again completes the circuit from ground through the relay ISi and over the simplex circuit of the pair RLi, through the upper winding of the polar relay Ci. Polar relay Ci now shifts its armature to its lower or front position and 40 this opens the circuit of the lower winding of the polar relay SW. The relay SW accordingly shifts its armature to its lower contact and the circuit from the jack Ji is now shifted from the transmitting line TL to the receiving line RL1 :45 and the caller is able to talk to the operator.

After the operator has completed the connection the caller may talk to the party with whom he is connected by operating the key K to transmit the carrier and releasing the key whenever .50 he wishes to hear the response of the called party.

The relay REC1 of course remains operated so long as the connection is established at the jack Ji. When the called party hangs up his receiver, 55 the operator may receive a disconnect signal and withdraw the plug from the jack Ji. This releases the relay Si, which in turn releases the relay S2. Relay S2, upon being restored to normal, opens the circuit of the relay RECi, which 60 releases and opens the circuit of relay SCO so that the apparatus is restored to normal.

It will, of course, be evident that when no call is being sent out from the ship station at D and with the apparatus at stations A and B in norS5 mal condition, the circuit L will be conditioned . to receive, as the lower winding of the polar relay SW will be open-circuited at the contacts of the relay S2 and corresponding relays. The biasing winding of said relay SW will therefore S. pull the armature to its lower contact, complete ing the circuit from the path L to the path RL.

S Under these conditions the marine operator at A may at any time signal the ship by plugging r into the jack Ji, thus energizing relays Si and S7 S2 in succession, so that a circuit is completed from ground over the back contact of relay SCO, over the middle back contact of the polar relay C1, the upper or back contact of the polar relay C1, and over the lower front contact of relay S2 through the lower winding of the polar relay SW. The current through the lower winding of the polar relay SW will shift its armature so that the path L will be connected to the transmitting path TL. The operator may now signal over the path TL by signaling equipment (not shown) and can, of course, talk over said path and through the radio transmitter ST at station C and radio station BR at station D in an obvious manner.

The dial equipment at ship station D and the step-by-step switching equipment at station B may be utilized for other purposes than those already described. For example, with the circuit as shown, the ship operator can send a signal to indicate dangers to navigation by dialing 80. This will cause the wiper Wi (or W2 as the case may be) to be elevated to the eighth row of contacts and stepped around to the tenth contact in that row, thus completing a circuit for the lamp DNL at the technical operator's position, and, if desired, other lamps may be connected to the same circuit located at other positions where it is desired that this signal shall appear. An urgent call may be indicated by dialing 07, which requires ten interruptions and 3 will step the switch wiper Wi to the tenth row, and the seven impulses following will step it around to the seventh contact in that row, completing the circuit in the urgent call lamp UCL.

This lamp, and other lamps on the same circuit 3 may be wired to appear at any desired point. A distress call may be made by dialing 03, in which case the wiper Wi will be stepped up in the tenth row and the third contact in that row, completing the circuit of the distress call lamp DCL, 4 which likewise may be wired to appear at any desired point. If it is desired to dial the technical operator directly without calling the marine operator a lamp TOL' may be actuated by dialing the code 70, for example. 4 Instead of lamps it will be understood that audible signals such as gongs may be used, or if preferred, both gongs and lamps may be employed.

What is claimed is: 60 1. In a ship shore radio telephone system, a land radio station having paths from a common terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection from the common terminal of said land radio station to a land circuit to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received from the ship station, and operable only when so conditioned to disable the radio receiver at the land station and to condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a supervisory signal device at the common terminal of said land station, and means to interrupt the carrier from the ship station in accordance with a code, said supervisory signal device at said common terminal being actuated only in response to said code.

2. In a ship shore radio telephone system, a land radio station having paths from a common terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection from the common terminal of said land radio station to a land circuit to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received from the ship station, and operable only when so conditioned to disable the radio receiver at the land station to condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a signal means at the land station responsive to a current of carrier frequency from the ship station or from an interfering station to produce 10 a signal at the land station, a supervisory signal device at the common terminal of said land station, means to interrupt the carrier from the ship station in accordance with a code, and means at the land station responsive to the code 5 but unresponsive to interference to actuate said supervisory signal device at said common terminal.

3. In a ship shore radio telephone system, a land radio station having paths from a common D terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio trans5 mitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection from the common terminal of said land station to a land circuit to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received from the ship station, and operable when so conditioned to disable the radio receiver at the land station and to condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a signal means at the land station responsive to a current of carrier frequency from the ship station or from an interfering station to produce a signal at the land station, a supervisory signal device at the common terminal of said land station, means at the ship station to interrupt the carrier sent out from the ship station in accordance with a code, a selective arrangement at the land station arranged to actuate said supervisory signal in response to the carrier frequency from the ship when interrupted in accordance with a particular code, but not actuating said signal in response to steady carrier, or carrier interrupted by a different code, or in response to interference.

4. In a ship shore radio telephone system, a land radio station having a normally disabled radio transmitter and a plurality of radio receivers each normally conditioned for operation, a short controlling and switching point at which connections may be completed from a land circuit to said transmitter and from any of said receivers to said land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means conditioned by the extension of a connection to a land circuit through said controlling and switching point to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received by one of said radio receivers at the land station, and operable only when so condi- 2g tioned to disable all of said radio receivers at the land station and condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a supervisory signal device at said switching point, and means 2 to interrupt the carrier from the ship station in accordance with a code to actuate said supervisory signal device at said switching point.

5. In a ship shore radio telephone system, a land radio station having a normally disabled 3 radio transmitter and a plurality of radio receivers each normally conditioned for operation, a shore controlling and switching point at which connections may be completed from a land circuit to said transmitter and from any of said receivers to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means conditioned by the extension of a connection to a land circuit through said controlling and switching point to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received by one of said radio receivers at the land station, and operable only when so conditioned to disable all of said radio receivers at the land station and condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a signal means at the land station responsive to a current of carrier frequency from the ship statio o an r from an interfering station to produce a signal at the land station, a supervisory signal device at said switching point, means to interrupt the carrier from the ship station in accordance with a code, and means at the land station responsive to the code but unresponsive to interference to actuate said supervisory signal device at said switching point.

6. In a ship shore radio telephone system, a land radio station having a normally disabled radio transmitter and a plurality of radio receivers each normally conditioned for operation, a shore controlling and switching point at which connections may be completed from a land circuit to said transmitter and from any of said receivers to said land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radi transmitter at the ship station to send out a car rier wave, means conditioned by the extension o a landward connection to a land circuit througi said controlling and switching point to.maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received by one of said radio receivers at the land station, and operable only when so conditioned to disable the radio receivers at the land station and condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a signal means at the land station responsive to a current of carrier frequency from the ship station or from an interfering station to produce a signal at the land station, a supervisory signal device at said switching point, means at the ship station to interrupt the carrier sent out from the ship station in accordance with a code, a selective arrangement at the land station arranged to actuate said supervisory signal device in response to the carrier frequency from the ship when interrupted in ac0 cornce with a particular code, but not actuating said signal in response to steady carrier, or carrier interrupted by a different code, or in response to interference.

7. In a ship shore radio telephone system, a land radio station having paths from a common terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection from the common terminal of said land radio station to a land circuit to maintain the radio transmitter at the land station in disabled con0 dition only when the carrier frequency is being received from the ship station, and operable only when so conditioned to disable the radio receiver at the land station and to condition the radio transmitter thereat for operation when no carrier 45is transmitted from the ship station, a supervisor signal device at the common terminal of said land station, means to interrupt the carrier from the ship station in accordance with a code, and means at the land station responsive to the code 60 but unresponsive to interference to actuate said supervisory signal device at said common terminal.

8. In a ship shore radio telephone system, a land radio station having paths from a common terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio transen mitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection from the common terminal of said land radio station to a land circuit to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being _ 70 received from the ship station, and operable only e when so conditioned to disable the radio receiver S at the land station and to condition the radio S transmitter thereat for operation when no carf rier is transmitted from the ship station, a suh 75 pervisory signal device at the common terminal of said land station, means at the ship station to interrupt the carrier sent out from the ship station in accordance with a code, a selective arrangement at the land station arranged to actuate said supervisory signal in response to the carrier frequency from the ship when interrupted in accordance with a particular code, but not actuating said signal in response to steady carrier, or carrier interrupted by a different code, or in response to interference. i 9. In a ship shore radio telephone system, a land radio station having a normally disabled radio transmitter and a plurality of radio receivers each normally conditioned for operation, a shore controlling and switching point at which connections may be completed from a land circuit to said transmitter and from any of said receivers to said land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means conditioned by the extension of a connection to a land circuit through said controlling and switching point to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received by one of said radio receivers at the land station, and operable only when so conditioned to disable all of said radio receivers at the land station and condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a supervisory signal device at said switching point, means to interrupt the carrier from the ship station in accordance with a code, and means responsive to the code but unresponsive to interference to actuate said supervisory signal device at said switching points.

ALBERT FRANKLIN BOWERS.