SIGNAL SWITCHING ARRANGEMENT
United States Patent 3792380
In a switching arrangement of the type having a plurality of coils simultaneously connected to a power source for causing movement of coil-associated switches, the addition of coil response time and release time adjusting means to control selective switching of two input signals to an output without incurring momentary signal interruption at the output. The response and release times are adjusted so that the switches associated with the signal to be connected to the output finish their movement before or at the same time as the start of movement of the switches associated with the signal to be disconnected from the output. The energization response time of each switch controlling relay coil is controlled by a variable resistance in series between the energizing source of power and the relay coil. The de-energization release time of each switch controlling relay coil is controlled by a variable resistance in parallel with said relay coil.
Inventors:
Murotani, Masayoshi (Sapporo, JA)
Yano, Tsunetoshi (Tateyama, JA)
Koyama, Kaoru (Tokyo, JA)
Motojima, Toshiharu (Tokyo, JA)
Yano, Tsunetoshi (Tateyama, JA)
Koyama, Kaoru (Tokyo, JA)
Motojima, Toshiharu (Tokyo, JA)
Application Number:
05/322665
Publication Date:
02/12/1974
Filing Date:
01/11/1973
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Export Citation:
Assignee:
Nippon Telegraph & Telephone Public Corporation (Tokyo, JA)
Nippon Electric Company, Limited (Tokyo, JA)
Nippon Electric Company, Limited (Tokyo, JA)
Primary Class:
Other Classes:
361/191, 361/159, 361/194
International Classes:
H01H47/00; H04B1/74; H01H47/04; H01H47/18; H01P1/10
Field of Search:
333/7,97S,98S 317/123,137,141,154,157 307/141 325/21,393
Primary Examiner:
Lawrence, James W.
Assistant Examiner:
Nussbaum, Marvin
Attorney, Agent or Firm:
Sughrue, Rothwell, Mion, Zinn & Macpeak
Claims:
We claim
1. In a signal switching arrangement having a driving circuit of a plurality of electromagnetic relays for selectively connecting one of two input circuits to one output terminal, a signal switching arrangement comprising a plurality of first variable impedance elements connected in series with a driving winding of each said relay, respectively, and a plurality of second variable impedance elements connected in parallel with each said relay, respectively, wherein said first and second variable impedance elements permit separate adjustment so as to control the response time of each said relay and to avoid the possible momentary interruption of a signal at said output terminal at the time of switchover. 2) A signal switching arrangement according to claim 1, wherein said plurality of relays comprise bridge-type and non-bridge-type relays, so combined as to avoid a variation in the output level of
1. In a signal switching arrangement having a driving circuit of a plurality of electromagnetic relays for selectively connecting one of two input circuits to one output terminal, a signal switching arrangement comprising a plurality of first variable impedance elements connected in series with a driving winding of each said relay, respectively, and a plurality of second variable impedance elements connected in parallel with each said relay, respectively, wherein said first and second variable impedance elements permit separate adjustment so as to control the response time of each said relay and to avoid the possible momentary interruption of a signal at said output terminal at the time of switchover. 2) A signal switching arrangement according to claim 1, wherein said plurality of relays comprise bridge-type and non-bridge-type relays, so combined as to avoid a variation in the output level of
Description:
The present invention relates to an arrangement for signal switching and, more particularly, to a mechanical switching arrangement utilizing electromagnetic relays for the basic frequency band circuit and/or intermediate frequency band circuit included in a microwave communication system.
Various types of switching arrangements for the switchover of microwave communication circuits have been proposed, including those employing diodes adapted to high-speed operation, and those others having electro-mechanical coaxial switches having mercury contact relays or reed relays exhibiting high stability and reliability in operation.
Among the switching elements, the mechanical coaxial switch has particularly high reliability. However, the conventional mechanical coaxial switch employes a plurality of relays, whose response characteristics or operational speed are different from one another. This tends to cause the momentary total interruption of signals at the time of switchover.
An object of the present invention is therefore to provide a signal switching arrangement adapted to avoid the above-mentioned momentary interruption of signals.
Another object of the present invention is to provide a novel signal switching arrangement for use in a stand-by switchover system, which is capable of avoiding the signal level variation even at the moment where the movable contact of the switch is momentarily in contact, so as to avoid the momentary interruption, with both the two fixed contacts coupled to the operating and stand-by transmission circuits.
According to the present invention, there is provided a signal switching arrangement comprising two signal input terminals, one signal output terminal, a predetermined number of switching contacts for selectively connecting one of said input terminals and the output terminal, and a plurality of electromagnetic relays for controlling said switching contacts, a first and a second variable impedance elements respectively connected in series and in parallel with the winding of each said relays, the impedances of said first and second variable impedance means being variable to thereby control the time for the response of the relays to their energization and release, whereby the momentary interruption of the signal is avoided.
An embodiment of the present invention employs, as said relays, two relays of different types, i.e., the bridge type and the non-bridge type, the former providing, in contrast to the latter, a temporary simultaneous connection between the movable contact and fixed contacts at the time of switchover.
The present invention will now be described in detail with reference to the accompanying drawings, in which:
FIGS. 1a and 1b illustrate typical examples of the conventional switching arrrangement employing coaxial switches;
FIG. 2 shows a fundamental relay circuit for explaining the principle of the present invention;
FIG. 3 illustrates the time response characteristics of the circuit shown in FIG. 2;
FIG. 4 shows an embodiment of the present invention having four relays;
FIG. 5 is a diagram showing the response time characteristics of the respective relays for the case where the embodiment of FIG. 4 is adjusted to form a non-momentary-interruption type switching arrangement;
FIG. 6 shows an equivalent circuit for illustrating the increase in the signal level at a load observed during the switchover period of the non-interruption type signal switch;
FIG. 7 is shows the response time characteristics of the respective relays employed in the circuit arrangement of the present invention;
FIG. 8 shows another equivalent circuit for illustrating the operation of the embodiment at the moment of the switchover; and
FIGS. 9a, 9b, and 9c show a schematic view illustrating the "bridge" formed between the movable contact and two fixed contacts of a mercury contact relay.
In FIG. 1 showing examples of conventioned circuits for selectively connecting one of the two input terminals A and B to one output terminal C, four electromagnetic relay windings RL 1 , RL 2 , RL 3 and RL 4 connected in parallel as shown in FIG. 1(a) are coupled to a power source E through a switch S. On the other hand, relay contacts rl 1 , rl 2 , rl 3 and rl 4 of the respective relays RL 3 .about. RL 4 are connected, as illustrated in FIG. 1(b), to form a network lying between the two input terminals A, B and the output terminal C. A resistor having resistance R 0 is inserted between the ground and one of the fixed contacts of each of the relays. The relays RL 1 .about. RL 4 respectively having the contacts rl 1 .about. rl 4 are of the coaxial type with the contacts connected to axical conductors of coaxial cables.
Under the state where the switch S is left open, the input terminal A is connected with output terminal C, with the movable contacts of rl 1 and rl 2 brought to contact with the upper fixed contacts thereof and with the other input terminal B terminated by the resistor R 0 . Upon the closure of the switch S to simultaneously energize relays RL 1 .about. RL 4 , the terminal B is connected to terminal C while terminal A is terminated by the resistor R 0 . As will be apparent from FIG. 1(b), the relays RL 2 and RL 4 are for avoiding the leakage of the switched-off input signal to the output terminal C.
In this circuit arrangement, it should be noted that the response speed is different from one relay to another. This results in the momentary interruption of the signal to be switched over.
In the principal part of the embodiment of the invention shown in FIG. 2, the response to the application and disconnection of the power supply is controlled by additional impedance elements. As shown in FIG. 2, the relay coil RL is shunted by a serially connected diode X and a variable resistor R p , with a variable resistor R s connected in series with the relay RL, a power source E and a switch S.
With the addition of the circuit elements X, R p and R s , the response speed of the relay RL becomes controllable as shown in FIG. 3, in which the resistance of resistor R p and R s is taken along the abscissa, while the response time is taken along the ordinate. The response time to the energization is controlled by adjusting the resistor R s as shown by curve 1 and the response to the release is controlled by the resistor R p as shown by curve 2. In this case, the response time of the relay RL to the energization is controlled by adjusting the variable resistor R s . The variable resistor R p connected in parallel with the relay RL does not serve to control the response time to the energization owing to the presence of the diode X which is connected in the reverse direction with respect to the applied voltage. In contrast with this, the response of the realy RL to the release is achieved by discharging through the shunt resistor R p the energy stored in its driving winding during the application of the power supply.
In the embodiment of the invention shown in FIG. 4, variable resistors RV 1 .about. RV 4 corresponding respectively to R s in FIG. 2, variable resistors RV 5 .about. RV 8 corresponding respectively to R p and diodes X 5 .about. X 8 corresponding respectively to X are additionally incorporated into the circuit. Further, diodes X 1 .about. X 4 are incorporated in order to effect the controls of the response times of the relays RL 1 .about. RL 4 to the release respectively independently. An ideal operation will now be explained as to the case where the non-bridge type switch is employed as each of the relays RL 1 .about. RL 4 . Under this state, the signal circuit A➝C in FIG. 1(b) is switched to the circuit B➝C without momentary interruption. Reference is made to a response time chart of the respective relays as shown in FIG. 5. Herein, the terms "the non-bridge type" denote a relay having mere switching construction of a single-pole double-throw type. In this chart, t 1 and t 2 denote starting points of the contacts rl 3 and rl 4 , respectively (the sequence of t 1 and t 2 is not restricted to this example). Time t 3 indicates motional completing points of the contacts rl 3 and rl 4 , which are also starting points of the contacts rl 1 and rl 2 . Times t 4 and t 5 represent completing points of the contacts rl 2 and rl 1 , respectively (the sequence of t 4 and t 5 is not restrictive). As seen from the drawing, the time lag between the starting time points of the contacts rl 1 and rl 2 over the completing time t 3 of the contacts rl 3 and rl 4 causes the signals to be overlapped within the period of the simultaneous connection of the movable contact with the fixed contacts. Conversely, if the former leads the latter, the momentary-interruption arises. If the response time of the relays RL 1 .about. RL 4 is appropriately controlled by adjusting the variable resistors RV 1 .about. RV 4 , the ideal switchover as shown in FIG. 5 is made possible. As regards the setting of the response time of the relays to the disconnection of the power supply as is performed in order to restore the state of the signal circuit after the switchover, quite the same principle is applied.
The ideal switching operation as shown in FIG. 5 is the most preferable for the signal switching arrangement. Practically, however, it is not easy to constantly maintain over a long period of time the mechanical stability of the contacts. Accordingly, a switching arrangement giving rise to non-momentary-interruption even in a longterm operation is suitable for such use. It is to be understood from the foregoing description that, in accordance with the present invention, the signal-overlap-type switching can also be easily realized by merely adjusting the variable resistors.
With such overlap-type switches, however, the two input signals simultaneously appear at the output during the switching operation. In order to flatten the level of the output signals in this case, reference is made to an equivalent circuit in which signals of quite the same phase are combined as shown in FIG. 6. In the figure, the level of the signal applied to a terminating load R 0 at an output terminal C becomes (2/3)I(1/2)I times higher to increase the level by 2.5 dB in comparison with that when one of signals is carried out. To avoid this defect, a mercury contact relay of the bridge type is employed as, e.g., relay RL 1 , and the response time of the respective relays to the energization are controlled as illustrated in FIG. 7. Then, as shown in the equivalent circuit at the signal combination in FIG. 8, the level variation of the signal applied to the load R 0 is avoided.
The bridge-type mercury contact relay comprises as its principal constituents a switching section with contacts, mercury and high-pressure hydrogen gas sealed into a glass tube. An armature is electro-magnetically driven by means of an electromagnetic coil disposed around the switching section. The contact section is always wetted by the capillary action of mercury, and the opening and closure of the circuit are effected by mercury. Therefore, the relay is perfectly free from chattering, and it has high mechanical stability and long life. FIG. 9 illustrates the "bridge" formed between the movable contact and two fixed contacts of the mercury contact relay, with FIG. 9(a) representing a position before motional starting, FIG. 9(b) illustrating an intermediate position of the transfer, and FIG. 9(c) showing a position after the completion of the operation. In the intermediate position, a movable contact is bridged at the central part with two fixed contacts due to the adsorption of mercury. Referring agin to FIG. 7, t 1 and t 2 are the same as in FIG. 5. Time t 3 designates the moment of the completion of the contacts rl 3 and rl 4 , and a mercury-bridge starting time of the contact rl 1 . Time t 4 indicates a starting time of the contact rl 2 ; t 5 , a time point at which the bridged mercury of the contact rl 1 is severed; and t 6 , the completion of the motion of the contact rl 2 . The sequence of the time points t 5 and t 6 is not restricted to the illustrated one. Herein, the period of time between t 3 and t 4 is determined to overlap the two input signals. During this period, the resistor R 0 connected to the make-contact of the contact rl 1 serves as a common load for the two signals. As shown in FIG. 8, a current of one-half I is caused to flow through the load R 0 at the point C, and it is of quite the same level at the time of the absence of combination. This principle is similarly applicable to the setting of the response time of the relays to the release. While the mercury contact relay has been herein referred to as the bridge-type relay, it is also possible to employ a relay so designed as to effect the bridging effect without resorting to mercury in the contact section.
Various types of switching arrangements for the switchover of microwave communication circuits have been proposed, including those employing diodes adapted to high-speed operation, and those others having electro-mechanical coaxial switches having mercury contact relays or reed relays exhibiting high stability and reliability in operation.
Among the switching elements, the mechanical coaxial switch has particularly high reliability. However, the conventional mechanical coaxial switch employes a plurality of relays, whose response characteristics or operational speed are different from one another. This tends to cause the momentary total interruption of signals at the time of switchover.
An object of the present invention is therefore to provide a signal switching arrangement adapted to avoid the above-mentioned momentary interruption of signals.
Another object of the present invention is to provide a novel signal switching arrangement for use in a stand-by switchover system, which is capable of avoiding the signal level variation even at the moment where the movable contact of the switch is momentarily in contact, so as to avoid the momentary interruption, with both the two fixed contacts coupled to the operating and stand-by transmission circuits.
According to the present invention, there is provided a signal switching arrangement comprising two signal input terminals, one signal output terminal, a predetermined number of switching contacts for selectively connecting one of said input terminals and the output terminal, and a plurality of electromagnetic relays for controlling said switching contacts, a first and a second variable impedance elements respectively connected in series and in parallel with the winding of each said relays, the impedances of said first and second variable impedance means being variable to thereby control the time for the response of the relays to their energization and release, whereby the momentary interruption of the signal is avoided.
An embodiment of the present invention employs, as said relays, two relays of different types, i.e., the bridge type and the non-bridge type, the former providing, in contrast to the latter, a temporary simultaneous connection between the movable contact and fixed contacts at the time of switchover.
The present invention will now be described in detail with reference to the accompanying drawings, in which:
FIGS. 1a and 1b illustrate typical examples of the conventional switching arrrangement employing coaxial switches;
FIG. 2 shows a fundamental relay circuit for explaining the principle of the present invention;
FIG. 3 illustrates the time response characteristics of the circuit shown in FIG. 2;
FIG. 4 shows an embodiment of the present invention having four relays;
FIG. 5 is a diagram showing the response time characteristics of the respective relays for the case where the embodiment of FIG. 4 is adjusted to form a non-momentary-interruption type switching arrangement;
FIG. 6 shows an equivalent circuit for illustrating the increase in the signal level at a load observed during the switchover period of the non-interruption type signal switch;
FIG. 7 is shows the response time characteristics of the respective relays employed in the circuit arrangement of the present invention;
FIG. 8 shows another equivalent circuit for illustrating the operation of the embodiment at the moment of the switchover; and
FIGS. 9a, 9b, and 9c show a schematic view illustrating the "bridge" formed between the movable contact and two fixed contacts of a mercury contact relay.
In FIG. 1 showing examples of conventioned circuits for selectively connecting one of the two input terminals A and B to one output terminal C, four electromagnetic relay windings RL 1 , RL 2 , RL 3 and RL 4 connected in parallel as shown in FIG. 1(a) are coupled to a power source E through a switch S. On the other hand, relay contacts rl 1 , rl 2 , rl 3 and rl 4 of the respective relays RL 3 .about. RL 4 are connected, as illustrated in FIG. 1(b), to form a network lying between the two input terminals A, B and the output terminal C. A resistor having resistance R 0 is inserted between the ground and one of the fixed contacts of each of the relays. The relays RL 1 .about. RL 4 respectively having the contacts rl 1 .about. rl 4 are of the coaxial type with the contacts connected to axical conductors of coaxial cables.
Under the state where the switch S is left open, the input terminal A is connected with output terminal C, with the movable contacts of rl 1 and rl 2 brought to contact with the upper fixed contacts thereof and with the other input terminal B terminated by the resistor R 0 . Upon the closure of the switch S to simultaneously energize relays RL 1 .about. RL 4 , the terminal B is connected to terminal C while terminal A is terminated by the resistor R 0 . As will be apparent from FIG. 1(b), the relays RL 2 and RL 4 are for avoiding the leakage of the switched-off input signal to the output terminal C.
In this circuit arrangement, it should be noted that the response speed is different from one relay to another. This results in the momentary interruption of the signal to be switched over.
In the principal part of the embodiment of the invention shown in FIG. 2, the response to the application and disconnection of the power supply is controlled by additional impedance elements. As shown in FIG. 2, the relay coil RL is shunted by a serially connected diode X and a variable resistor R p , with a variable resistor R s connected in series with the relay RL, a power source E and a switch S.
With the addition of the circuit elements X, R p and R s , the response speed of the relay RL becomes controllable as shown in FIG. 3, in which the resistance of resistor R p and R s is taken along the abscissa, while the response time is taken along the ordinate. The response time to the energization is controlled by adjusting the resistor R s as shown by curve 1 and the response to the release is controlled by the resistor R p as shown by curve 2. In this case, the response time of the relay RL to the energization is controlled by adjusting the variable resistor R s . The variable resistor R p connected in parallel with the relay RL does not serve to control the response time to the energization owing to the presence of the diode X which is connected in the reverse direction with respect to the applied voltage. In contrast with this, the response of the realy RL to the release is achieved by discharging through the shunt resistor R p the energy stored in its driving winding during the application of the power supply.
In the embodiment of the invention shown in FIG. 4, variable resistors RV 1 .about. RV 4 corresponding respectively to R s in FIG. 2, variable resistors RV 5 .about. RV 8 corresponding respectively to R p and diodes X 5 .about. X 8 corresponding respectively to X are additionally incorporated into the circuit. Further, diodes X 1 .about. X 4 are incorporated in order to effect the controls of the response times of the relays RL 1 .about. RL 4 to the release respectively independently. An ideal operation will now be explained as to the case where the non-bridge type switch is employed as each of the relays RL 1 .about. RL 4 . Under this state, the signal circuit A➝C in FIG. 1(b) is switched to the circuit B➝C without momentary interruption. Reference is made to a response time chart of the respective relays as shown in FIG. 5. Herein, the terms "the non-bridge type" denote a relay having mere switching construction of a single-pole double-throw type. In this chart, t 1 and t 2 denote starting points of the contacts rl 3 and rl 4 , respectively (the sequence of t 1 and t 2 is not restricted to this example). Time t 3 indicates motional completing points of the contacts rl 3 and rl 4 , which are also starting points of the contacts rl 1 and rl 2 . Times t 4 and t 5 represent completing points of the contacts rl 2 and rl 1 , respectively (the sequence of t 4 and t 5 is not restrictive). As seen from the drawing, the time lag between the starting time points of the contacts rl 1 and rl 2 over the completing time t 3 of the contacts rl 3 and rl 4 causes the signals to be overlapped within the period of the simultaneous connection of the movable contact with the fixed contacts. Conversely, if the former leads the latter, the momentary-interruption arises. If the response time of the relays RL 1 .about. RL 4 is appropriately controlled by adjusting the variable resistors RV 1 .about. RV 4 , the ideal switchover as shown in FIG. 5 is made possible. As regards the setting of the response time of the relays to the disconnection of the power supply as is performed in order to restore the state of the signal circuit after the switchover, quite the same principle is applied.
The ideal switching operation as shown in FIG. 5 is the most preferable for the signal switching arrangement. Practically, however, it is not easy to constantly maintain over a long period of time the mechanical stability of the contacts. Accordingly, a switching arrangement giving rise to non-momentary-interruption even in a longterm operation is suitable for such use. It is to be understood from the foregoing description that, in accordance with the present invention, the signal-overlap-type switching can also be easily realized by merely adjusting the variable resistors.
With such overlap-type switches, however, the two input signals simultaneously appear at the output during the switching operation. In order to flatten the level of the output signals in this case, reference is made to an equivalent circuit in which signals of quite the same phase are combined as shown in FIG. 6. In the figure, the level of the signal applied to a terminating load R 0 at an output terminal C becomes (2/3)I(1/2)I times higher to increase the level by 2.5 dB in comparison with that when one of signals is carried out. To avoid this defect, a mercury contact relay of the bridge type is employed as, e.g., relay RL 1 , and the response time of the respective relays to the energization are controlled as illustrated in FIG. 7. Then, as shown in the equivalent circuit at the signal combination in FIG. 8, the level variation of the signal applied to the load R 0 is avoided.
The bridge-type mercury contact relay comprises as its principal constituents a switching section with contacts, mercury and high-pressure hydrogen gas sealed into a glass tube. An armature is electro-magnetically driven by means of an electromagnetic coil disposed around the switching section. The contact section is always wetted by the capillary action of mercury, and the opening and closure of the circuit are effected by mercury. Therefore, the relay is perfectly free from chattering, and it has high mechanical stability and long life. FIG. 9 illustrates the "bridge" formed between the movable contact and two fixed contacts of the mercury contact relay, with FIG. 9(a) representing a position before motional starting, FIG. 9(b) illustrating an intermediate position of the transfer, and FIG. 9(c) showing a position after the completion of the operation. In the intermediate position, a movable contact is bridged at the central part with two fixed contacts due to the adsorption of mercury. Referring agin to FIG. 7, t 1 and t 2 are the same as in FIG. 5. Time t 3 designates the moment of the completion of the contacts rl 3 and rl 4 , and a mercury-bridge starting time of the contact rl 1 . Time t 4 indicates a starting time of the contact rl 2 ; t 5 , a time point at which the bridged mercury of the contact rl 1 is severed; and t 6 , the completion of the motion of the contact rl 2 . The sequence of the time points t 5 and t 6 is not restricted to the illustrated one. Herein, the period of time between t 3 and t 4 is determined to overlap the two input signals. During this period, the resistor R 0 connected to the make-contact of the contact rl 1 serves as a common load for the two signals. As shown in FIG. 8, a current of one-half I is caused to flow through the load R 0 at the point C, and it is of quite the same level at the time of the absence of combination. This principle is similarly applicable to the setting of the response time of the relays to the release. While the mercury contact relay has been herein referred to as the bridge-type relay, it is also possible to employ a relay so designed as to effect the bridging effect without resorting to mercury in the contact section.