JPS6033328B2 - Bipolar signal switching circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bipolar signal switching circuit that performs switching between a working communication device and a backup communication device that send out bipolar signals.

Conventionally, when switching between a working communication device that sends bipolar signals and a standby communication device, it has been common to use a relay.

For example, as shown in FIG. 1, the output sides of the working communication device 1 and the backup communication device 2 are connected to the output terminal 3 via relay contacts SW1 and SW2, so that when a failure occurs in the working communication device 1, By turning off the relay contact SWI and turning on the contact SW2, the communication is switched from the working communication device 1 to the standby communication device 2.
It will be switched to. However, since the switching operation time of the relay is on the order of milliseconds, when a high-speed bipolar signal is being sent out, the instantaneous interruption time when switching between the active and standby signals cannot be ignored. Furthermore, since relays perform mechanical operations, they do not have sufficient reliability after a long period of time. The present invention has been made to improve the above-mentioned drawbacks of the prior art, and its object is to quickly switch between active and standby devices in a hot standby configuration that transmits bipolar signals.

Examples will be described in detail below. FIG. 2 is a circuit diagram of a main part of an embodiment of the present invention, in which a working communication device 11 and a standby communication device 12 constitute a PCM communication device with a hot standby configuration, and a bipolar signal is sent from an output terminal 13. be done.

Further, 14 to 19 are transistors, 20 and 21 are output transformers, and a power supply voltage of 10 V is applied to the middle point of the primary side of the output transformers 20 and 21, and the secondary side is connected in parallel to the output terminal 13. has been done. The bipolar signal output circuit is
Push-pull transistors 14 to 17 connected to the primary sides of balanced output transformers 20 and 21 are connected to signals A,
The configuration is controlled by A', B, and B', and is shown in Fig. 3 A (
As shown in A') and B(B'), signals A and A' are applied to the bases of transistors 4 and 16, and signals B and B' are applied to the bases of transistors 5 and 17, respectively, and the base of transistor 18 is applied to When the control signal C applied to the transistor 19 is set to the /· level and the control signal 0 applied to the base of the transistor 19 is set to the low level, the output OUTI on the secondary side of the output transformer 20 becomes a bipolar signal as shown by OUT in FIG. In the backup communication device 12, since the transistor 19 is off, the signals A' and B' also turn off the transistors 16 and 17, so the impedance seen from the secondary side of the output transformer 21 becomes infinite, and the output transformer This has no effect on the amplitude of the output UTI of No. 20. Also, the control signal C is set to low level, and the control signal C'
When is set to a high level, transistor 18 is turned off, and since transistors 14 and 15 are also turned off by signals A and B, the impedance seen from the secondary side of output transformer 20 becomes infinite, and transistor 19 is turned on. Accordingly, transistors 16 and 1 are activated in response to signals A' and B'.
7 is turned on and off, the output OUT2 on the secondary side of the output transformer 21 becomes a bipolar signal as shown by OUT2 in FIG.

As mentioned above, the control signals C and O are used to switch between the active and standby configurations in the hot standby configuration, and this switching is performed at a time corresponding to the operating speed of the transistors 18 and 19, which is easily available outside high-speed operating transistors. Because of this, high-speed switching is possible.

Furthermore, even if the secondary sides of the output transformers 20 and 21 are connected in parallel, the impedance of one of them becomes infinite, so there is no adverse effect on the amplitude of the output signal. As explained above, the present invention connects the push-pull transistors 14 to 17 to the primary sides of the output transformers 20 and 21 of the active communication device 11 and the standby communication device 12 that output bipolar signals and have a hot standby configuration. Transistors 18 and 19, which are turned on and off by control signals C and C', are connected to the common emitter, and one of these transistors 18 and 19 is turned on and the other is turned off, thereby controlling the current communication device 11. and the backup communication device 12 are set in an operating state and the other is in an inoperable state, and the switching between the active and standby communication devices is enabled by the control signals C and C', and the transistors 18 and 19 are Since it operates at high speed, high-speed switching is possible.

Also, since the output transformer in the non-operating state has infinite impedance when viewed from the output side, simply connecting the secondary sides of the output transformers 20 and 21 in parallel will not affect the amplitude of the output bipolar signal. Therefore, high-speed switching between active and standby signals can be performed with a simple configuration, and therefore high-speed/dipolar signal switching is also possible.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of conventional switching between working and standby signals that send out bipolar signals, FIG. 2 is a schematic circuit diagram of an embodiment of the present invention, and FIG. 3 is an explanatory diagram of the moving signal of FIG. 2. 11 is a working communication device, 12 is a backup communication device, 13 is an output terminal, 14 to 19 are transistors, and 20 and 21 are output transformers. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a circuit that performs switching between a working communication device and a backup communication device in a hot standby configuration that outputs bipolar signals, one of the output transformers of the working communication device and the backup communication device
A transistor that is turned on and off by a control signal is connected to the common emitter of the pushable transistor connected to the next side, and the secondary sides of the output transformers of the working communication device and the standby communication device are connected in parallel. A bipolar signal switching circuit characterized by: