JPS6251013B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a clock distribution system switching system for detecting a failure in a working clock distribution system in a PCM terminal station and switching to a protection system.

FIG. 1 shows a conventional example of a clock distribution system switching system. In the figure, 1 is the terminal device, 2 is the clock source (DCS) of the terminal device 1, and the basic clock supplied from the clock source 2 is distributed to the working clock distribution board 3 and the standby clock distribution in the terminal device 1. Enter board 4. The clock distribution boards 3 and 4 have the same circuit, and the working clock distribution board 3 is normally used. Various clocks output from the clock distribution board 3 are supplied to each system 6, 7, . . . , n via a switch 5. Here, each system 6, 7, . . . , n has the same configuration. When a failure occurs in the active system clock distribution board 3, the switching control signal S _A is sent by the monitoring circuit A to the switch 5 to switch to the backup system clock distribution board 4, and the clock is transferred from the backup system clock distribution board 4. The output various clocks are supplied to each system 6, 7, . . . , n.

FIG. 2 shows another conventional example of a clock distribution system switching system, in which the same reference numerals as in FIG. 1 indicate the same components. The clock distribution board is duplicated as in the previous example, and if a failure occurs in the active system clock distribution board 3, the switching control signal S _A drives the switch 5 by the function of the monitoring circuit A, and the backup system clock is switched on. Switch to distribution board 4. The clock distribution boards 3 and 4 are further divided into clock receiving sections x ₃ and x ₄ and timing pulse generation boards y ₃ and y ₄ . The operation of the clock receivers x ₃ and x ₄ is the same as that of the clock distribution boards 3 and 4 in FIG. In the case of Fig. 1, each system 6, 7, ..., n has a timing pulse generator, but in the synchronous terminal station 1, the transmitting and receiving clocks are synchronized. Since the various timing pulses can be used in common in all systems, they are stored in the clock distribution boards 3 and 4 and made common to all systems. The basic clock coming from the clock source 2 enters a clock distribution board 3, 4, where various timing pulses are generated and supplied via a switch 5 to each system 6, 7, . . . , n.

However, the monitoring circuit must monitor all clock or timing pulses supplied to each system from the clock distribution board. This is because even if any one clock or timing pulse becomes abnormal, the entire system will be affected. The amount of hardware required for this monitoring is quite large, especially when the timing pulse generator is made common to the entire system as in the second conventional example.

SUMMARY OF THE INVENTION Therefore, the present invention aims to improve the above-mentioned drawbacks of the prior art, and its purpose is to provide a clock distribution system switching system that detects failures in the clock distribution system and controls switching from the active system to the standby system with a simple configuration. It's about doing. A feature of the present invention for achieving this object is to supply various clocks to a plurality of systems via a first clock distribution system, and to operate a changeover switch in response to a failure of a clock in the first clock distribution system. In the PCM terminal equipment that automatically switches to the second clock distribution system and supplies clocks to each system from the second clock distribution system, the first
Detecting alarms with the same contents occurring in a plurality of systems in response to a clock failure in a clock distribution system, and generating a switching control signal to operate a changeover switch when the alarm occurs in all of the plurality of systems. This is a clock distribution system switching method in which the clock distribution system is switched to the second clock distribution system.

Examples will be described below with reference to the drawings.

FIG. 3 shows a first embodiment of the clock distribution system switching system according to the present invention, in which the clock source 2 of the terminal equipment 1 is connected to the working system clock distribution board 3 and the standby system clock distribution board 4, and the clock distribution board 3, 4 are connected to each system 6, 7, . . . , n via a changeover switch 5, respectively. The changeover switch 5 switches each system 6, 7,
AND circuit 8 which inputs the alarm generated by ..., n
a, 8b and the outputs of the AND circuits 8a, 8b are controlled by the output SA obtained through the OR circuit 9, and when the clock in the working system clock distribution board 3 is abnormal, the clock is sent to the standby system clock distribution board 4. Each system 6, 7, . . . , n is configured to be connected.
In this embodiment, it is assumed that each system has its own timing pulse generator.

Assume that in the above configuration, the clocks supplied from the clock distribution boards 3, 4 to the systems 6, 7, . When an abnormality occurs in these clocks, each system always generates some sort of alarm. That is, if there is an abnormality in the transmission line interface clock, an abnormality will occur in the synchronization pattern, and a game alarm a _s will be sent from the opposing station. Furthermore, if an abnormality occurs in the encoder/decoder clock, an abnormality will occur in the operation of the encoder/decoder in each system 6, 7,..., n, and the encoder/decoder monitoring circuit (not shown) will cause an alarm in the encoder/decoder. utter a _c .
These alarms issued when the clock is abnormal are common to all systems 6, 7,..., n, so the alarms a _s and a _c are logically ANDed for all systems.
If the results are obtained by AND circuits 8a and 8b and then logically summed by OR circuit 9, a signal S _A indicating a clock abnormality is obtained. When the changeover switch 5 is driven using this as a switching control signal, switching from the active system clock distribution board 3 to the standby system clock distribution board 4 is performed.

The above describes the case where there are two types of clocks, but even if a clock used for another purpose is added, monitoring and alarms are attached to the functions operated by that clock, so switching can be performed in the same way as described above. The switch 5 can be controlled.

FIG. 4 shows a second embodiment of the clock distribution system switching system according to the present invention, and shows an example of application of the present invention in a case where the timing pulse generator is common to the entire system. That is, in the active system clock distribution board 3 and the standby system clock distribution board 4, in addition to the clock receiving sections x ₃ and x ₄ as described in FIG. 2, timing pulse generation boards y ₃ and y ₄ are provided. The other configurations are the same as the first embodiment.

With the above configuration, various timing pulses are supplied from the clock distribution board 3 to each system 6, 7, ..., n. However, if an abnormality occurs in any of the pulses, the above-mentioned first An alarm is issued as in the embodiment. Therefore, if the AND circuits 8a and 8b take the logical product of each alarm, and the OR circuit 9 takes the logical sum of the outputs of the circuits 8a and 8b, the changeover switch 5 will be activated in the same manner as in the first embodiment.
It is possible to switch from the active clock distribution board 3 to the standby clock distribution board 4 via.

As explained above, in the clock distribution system switching system according to the present invention, the monitoring and alarm functions in each system are activated whenever there is an abnormality in the clock related to each monitored area, and issue a game alarm, code/decoder alarm, etc. By taking advantage of this property, when an alarm appears in the entire system, it is determined that there is an abnormality in the clock, and the switch is switched to the standby clock distribution panel.Therefore, there is no need to add a circuit for clock monitoring, and switching control is possible. This has the advantage that the amount of hardware added for this purpose is extremely small and the configuration is simple.

[Brief explanation of the drawing]

FIG. 1 shows a conventional example of a clock distribution system switching system, FIG. 2 shows another conventional example of a clock distribution system switching system, FIG. 3 shows a first embodiment of a clock distribution system switching system according to the present invention, and FIG. A second embodiment of the clock distribution system switching system according to the present invention is shown. DESCRIPTION OF SYMBOLS 1... Terminal equipment, 2... Clock source, 3... Working system clock distribution board, 4... Standby system clock distribution board, 5...
Changeover switch, 6, 7 to n...Each system, A...Clock or timing pulse monitoring circuit, x ₃ ...Clock receiver (active system), x ₄ ...Clock receiver (standby system), y ₃ ...Common timing pulse generation board (active system), y ₄ ... Common timing pulse generator board (standby system), S _A ... switching control signal, a _s ... game alarm, a _c
...Code decoder alarm, 8a, 8b...AND circuit, 9
...OR circuit.

Claims (1)

[Claims] 1. Supplying various clocks to a plurality of systems via a first clock distribution system, and automatically switching to a second clock distribution system by operating a changeover switch in response to a clock failure in the first clock distribution system; A PCM terminal device that supplies various clocks to each system from the second clock distribution system detects an alarm with the same content occurring in multiple systems in response to a clock failure in the first clock distribution system, and A clock distribution system switching method characterized in that, when a clock distribution system occurs in all of the plurality of systems, a switching control signal is generated and a changeover switch is operated to switch to a second clock distribution system.