SU470089A1 - Call signal receiver - Google Patents

Description

one

The invention relates to a telephone communication technique, in particular, to signaling devices.

Call signal receivers are known that operate on the principle of allocating a ring frequency by counting the number of periods of the input signal over a fixed period of time.

These receivers are used to operate at tonal frequencies, which leads to a significant complication of their circuit due to the need to protect the receiver from false triggering when variable-frequency signals arrive at its input. In addition, in order to transmit a call signal at the far end of the line, when making a call with a tone frequency, it is necessary to have a stable generator, which leads to additional difficulties when working on malfunctioning PBX lines taken at the control in the cross-country, as in the set of devices used by the electrician when operating on a faulty line, such generators are not included.

As a call signal generator, an electrician can use a handset with a dialer, usually used when checking telephone exchanges.

The duration of the call signal should exceed twice the period of operation of the generator

a calibrated duration triggered out of sync with the arrival of a call signal, which completely eliminates the possibility of using a dialer as a call signal generator.

The counter is triggered by the leading edge of the generator pulse with a calibrated duration, since, if there is a control signal at its input at the moment of resetting the control signal

malfunction, which, if a sufficiently short series of pulses are sent using the dialer, can lead to a failure of the call signal. The purpose of the invention is to improve the noise immunity of the call signal receiver.

The proposed receiver is different in that it additionally introduces a pulse width measuring node and a delay circuit, the output of the pulse shaper is connected via a pulse width measuring node to the corresponding generator input of a calibrated duration and to the "Reset Counter, which, in turn, is connected to a delay circuit controlling the generator output of a calibrated duration.

The block diagram of the reception of the call signal is shown in the drawing.

The receiver contains a pulse former 1, a selector 2, a counter 3, a decoder 4,

a generator of calibrated duration 5, a delay circuit 6, a coincidence circuit 7, an actuating element 8, a pulse duration measuring circuit 9.

The receiver of the call signal works as follows.

In the initial state of the former 1, a supply voltage is supplied to the line. When a handset is connected or if there is a shunt on the line, direct current begins to flow through the receiving elements of the driver, which prepares the driver to receive the call signal pulses.

When the dialer dials the number corresponding to the call signal, a square pulse will appear at the output of the driver. The leading edge of the first pulse is triggered by a generator of a calibrated duration 5 and a pulse duration measuring circuit 9. The generator 5 supplies a control signal to the selector 2, which connects the pulse counter 3 to the output of the shaping device 1. The pulses coming from the shaping device 1 to the counter 3 are fixed by a counter in generator dwell time If during this time the counter receives the number of pulses corresponding to the call signal, from the decoder 4 to the coincidence circuit 7 a signal will be received allowing the actuator 8 to turn on. At the end of the generator 5, the second input of the coincidence circuit 7 is sent a control signal leading to actuation actuator 8.

The counter 3 is reset by a pulse from the delay circuit 6, which starts when the generator 5 returns to its initial state. The delay time of the reset pulse removed from the output of circuit 6 is determined by the time required for the actuator 8 to operate reliably.

The leading edge of each pulse from the former 1 starts the measurement circuit for the duration of the pulse 9. If the pulse duration complies with the standards set for the dialers, the output

scheme 9, the signal is absent, and the counter 3 continues to count the pulses arriving at its input. When entering the circuit 9 pulse, the duration of which does not match

to the established standards, the output of circuit 9 is a signal that translates counter 3 and a generator of calibrated duration 5 to the initial state. From the above, it is clear that when conducting

work on the line taken at the control cross, any pulse changes in the line state do not lead to a false call signal, because the probability of the appearance of a pulse sequence with

parameters and the number of pulses for the set time is almost zero.

Thus, the introduction into the receiver circuit of the call signal of the pulse duration measuring circuit 9 and the delay circuit 6 can significantly increase the noise immunity of the receiver when using the dialer as a generator of the call signal.

Subject invention

The receiver of the call signal containing the serially connected pulse driver, selector, counter, decoder,

a coincidence circuit and an execution node, the output of the pulse generator connected to the control input of the selector via a calibrated duration generator, the control output of which is connected to

the second input of the coincidence circuit, characterized in that, in order to improve the noise immunity of the receiver, a pulse duration measuring node and a delay circuit are additionally introduced, the output of the pulse shaper is connected via a pulse width measuring node to the corresponding generator input of the calibrated duration and to the "Reset Counter which, in turn, is connected via

a delay circuit controlling the generalizer output of a calibrated duration.

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