JPH0834642B2 - Communication system between digital exchanges - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital exchange, and more particularly to a specific time slot in a multiplexed signal transmitted on a multiplex transmission line (highway) in synchronization with a clock signal. The present invention relates to a communication system between a digital exchange that sends out a data signal and a digital exchange that takes in the data signal from a specific time slot.

[Prior Art] Conventionally, a digital exchange of this type is interposed between a telephone and a multiplex transmission line. The multiplex transmission line is a transmission line that transmits a multiplexed signal including a plurality of time slots at a specific transmission rate.

The telephone transmits and receives analog data signals such as voice signals. A CODEC that converts the data signal into a digital data signal between the telephone and the digital exchange in order to input / output the data signal to / from the digital exchange.
(Encoding / decoding device) is required.

Each digital exchange receives a data signal from a CODEC (encoding / decoding device) and transmits it in a predetermined time slot in the multiplexed signal on the multiplex transmission path, or transmits a data signal from a desired time slot in the multiplexed signal. It has a function as a time-division switch that gives the timing to take in.

Considering the case where a data signal is transferred from the telephone of A to the telephone of B, as shown in FIG. 3, for example, in a digital exchange of A, data to a predetermined time slot in a multiplex signal on a multiplex transmission line is transmitted. The signal transmission timing is given by the leading edge a here of the corresponding clock pulse in the clock signal having the frequency corresponding to the transmission speed of the multiplex transmission line, here, the rising edge a.

On the other hand, in B's digital exchange, the data signal in the same time slot in the multiplexed signal is taken in, but at that timing, it is given by the trailing edge of the same clock pulse, here the falling edge b.

By the way, when the degree of multiplexing of the multiplexed signal is increased, the transmission speed is increased, the frequency of the clock signal is increased accordingly, and the time t from the transmission timing of the data signal to the acquisition timing is also reduced. Therefore, if the delay on the circuit from the exchange to the exchange is large, there is a disadvantage that the data signal cannot be taken in from a desired time slot.

In FIG. 4, the multiplicity of time slots on the highway is the same as that in FIG. 3, and the case where the frequency of the clock signal is doubled is illustrated.

In this case, in A, after transmitting the data signal to the predetermined time slot in synchronization with the leading edge c of the clock pulse, when the data signal is taken in by B, at the timing of the trailing edge e of the next clock pulse. It is capturing the data signal.

At this time, the time t from the data signal sending timing c to the fetch timing e is 1.5 compared with the case of FIG.
It is doubled (t = t ₂ ), and the time t until the fetch timing can be afforded, so that the problem of delay is greatly improved.

[Problems to be Solved by the Invention] However, if the frequency of the clock signal is doubled, noise is likely to occur, and reception of a desired electromagnetic signal may be impaired, so that malfunction due to noise may occur. growing. That is, EMI (electomagnetic int
erference) It was not preferable as a countermeasure.

Therefore, the technical problem of the present invention is to eliminate the above-mentioned drawbacks of noise generation, and to provide a digital exchange having a sufficient time from the transmission timing of a data signal to a specific time slot in a multiplexed signal on a multiplex transmission path to the acquisition timing. It is to provide a communication system between.

[Means for Solving the Problems] According to the present invention, a multiplexing transmission line for transmitting a multiplexed signal composed of a plurality of time slots at a predetermined transmission rate, and a clock pulse train repeating at a frequency corresponding to the transmission rate are provided. A first clock signal generating means for outputting a first clock signal; and a data signal in synchronization with a leading edge of a clock pulse which receives the first clock signal and corresponds to a predetermined time slot in the multiplexed signal. To the predetermined time slot, and a second digital exchange to take in the data signal from the predetermined time slot, whereby the data signal is transferred to the first digital exchange. In the communication system between the digital exchanges, the communication is performed from the digital exchange to the second digital exchange via the multiplex transmission path. It has a second clock signal generating means for outputting a second clock signal consisting of a clock pulse train which has the same frequency as the first clock signal and repeats with a predetermined phase difference from the clock pulse, and the second digital signal is provided. The exchange receives the second clock signal and synchronizes with the predetermined edge of the clock pulse in the second clock signal corresponding to the predetermined time slot in the multiplexed signal on the multiplex transmission line. A communication system between digital exchanges is obtained, which is characterized in that the data signal is taken in from a time slot.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

With reference to FIG. 1, in a communication system between digital exchanges according to an embodiment of the present invention, a multiplex transmission line 1, a clock generator unit 2, a control line 3, a CODEC 8 connected to a telephone of an instep, a digital signal Switch 9 and control circuit
It has a CODEC 8 ', a digital exchange 9', and a control circuit 10 'which are connected to the second party's telephone.

The multiplex transmission path 1 is a predetermined transmission speed (eg, frequency 4.096 MHz) of a multiplexed signal obtained by multiplexing a plurality of time slots.
To transmit.

The clock generator unit 2 outputs a first clock signal composed of a clock pulse train that repeats at the same frequency (4.096 MHz) as the transmission speed of the multiplex transmission line 1
And a second clock signal for outputting a second clock signal composed of a clock pulse train having the same frequency (4.096 MHz) as the first clock signal but repeating with a predetermined phase difference θ. Generating means 6 and an operation for giving the timing of the first time slot 0 of the time slots having a time series from time slot 0 to time slot 511 in the multiplexed signal on the multiplex transmission path 1, that is, It has a frame clock signal generating means 7 for generating a frame clock signal (its frequency is, for example, 8 kHz) for performing frame synchronization.

In the case of the conventional example shown in FIG. 3 and FIG. 4, the clock signal generating means is only one of 5 or 6 and generates one kind of clock signal of the above-mentioned frequency. In this case, since only one clock pulse generator is required, there is an advantage that the circuit is simple, but on the other hand, there are drawbacks as described above.

Instep A control circuit 10 is connected to control circuit 1
It is connected to 0 '. In the control circuit 10 of the instep, CODEC8,
When the analog signal transmission information is received via the digital exchange 9, the control circuit 10 of the customer A outputs a command to the control circuit 10 'of the customer B via the control line 3 to fetch the transmission information.

The CODECs 8 and 8'receive the transmission information of the analog signal and convert it into a digital data signal, and conversely, receive the digital data signal and convert into an analog data signal.

The digital exchanges 9 and 9'receive the data signal while receiving the frame clock signal, the first and second clock signals from the clock generator unit 2,
Rising edge of the clock pulse of the first clock signal (leading edge)
In synchronism with the above, the data signal is transmitted to a predetermined time slot in the multiplexed signal on the multiplex transmission line 1, or
The data signal is taken in from a predetermined time slot in synchronization with the trailing edge of the pulse of the second clock signal.

 Consider the case where a data signal is sent from Party A to Party B.

Since the data signal from the instep A is analog, it is converted to digital through the CODEC 8 and then sent to the digital exchange 9. The digital data signal is sent from the digital exchange 9 to a predetermined time slot in the multiplexed signal on the multiplex transmission line 1 in synchronization with the rising edge f of the clock pulse of the first clock signal.

In the digital exchange 9 ', the frame clock signal and the first and second clock signals are received from the clock generator unit 2. The control circuit 10 'is a control circuit
Upon receiving an instruction to take in the data signal from 10, the digital exchange 9'is instructed to take the data signal.

The digital exchange 9'takes in the data signal from the predetermined time slot in synchronization with the falling edge g of the clock pulse of the second clock signal. Since this data signal is digital, it is converted to analog via CODEC 8'and sent to B.

In this way, the analog data signal of A is transmitted to B.

[Effects of the Invention] As is clear from the above description, according to the present invention, the first frequency having the same frequency as the transmission rate of the multiplexed signal on the multiplex transmission path is used.
Of the first clock signal and the second clock signal having a phase difference different from that of the first clock signal, the data is synchronized with the leading edge of the pulse of the first clock signal. The signal is sent to a predetermined time slot in the multiplexed signal, and the data signal is taken from the time slot in synchronization with the trailing edge of the pulse of the second clock signal. Since a long margin corresponding to the phase difference can be provided from the time to the timing of taking in, the problem due to the delay of signal transmission is significantly improved, and therefore even if the transmission speed is high, the delay as a circuit element is small. There is an effect that a relatively large element can be used without having to select an element.

[Brief description of drawings]

FIG. 1 is a diagram showing a communication system between digital exchanges according to an embodiment of the present invention, and FIG. 2 is a diagram showing a time chart of the first and second clock signals and the multiplex transmission line in FIG. FIG. 3 is a diagram showing a time chart of the clock signal and the multiplex transmission line of the conventional digital exchange, and FIG. 4 is the time between the clock signal and the multiplex transmission line when the frequency of the clock signal of FIG. 3 is doubled. It is a figure which shows a chart. 1 ... Multiplex transmission line, 2 ... Clock generator unit, 3 ... Control line, 5 ... First clock signal generating means, 6 ... Second clock signal generating means, 7 ... Frame clock signal generating means , 8,8 ′ …… CODEC, 9,9 ′ ……
Digital exchange, 10, 10 '... control circuit.

Claims (1)

[Claims] 1. A first transmission circuit for outputting a first clock signal composed of a multiplex transmission line for transmitting a multiplexed signal composed of a plurality of time slots at a predetermined transmission rate, and a clock pulse train repeating at a frequency corresponding to the transmission rate. Receiving the first clock signal and transmitting the data signal to the predetermined time slot in synchronization with the leading edge of the clock pulse corresponding to the predetermined time slot in the multiplexed signal. It has a first digital exchange and a second digital exchange that takes in the data signal from the predetermined time slot, whereby the data signal is transmitted from the first digital exchange through the multiplex transmission path. In the communication system between the digital exchanges, which is adapted to transmit to the second digital exchange, the same frequency as the first clock signal is used. A second clock signal generating means for outputting a second clock signal composed of a clock pulse train which is repeated with a predetermined phase difference from the clock pulse, and the second digital exchange has the second clock signal. And receiving the data signal from the predetermined time slot in synchronization with the trailing edge of the clock pulse in the second clock signal corresponding to the predetermined time slot in the multiplexed signal on the multiplex transmission path. A communication system between digital exchanges having a configuration.