JPS5930344B2 - Encoder-decoder monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an encoder-decoder monitoring system that monitors the operation of an encoder and decoder that perform mutual conversion between analog and digital signals.

Conventionally, various methods have been known as this type of monitoring method, but as a typical method, the monitoring method disclosed in the 1975 IEICE national conference paper draft, page 1552, is shown in Figure 1. Let me explain this.

In FIG. 1, an analog signal input to terminal 1 has high frequency components suppressed by a filter 10, passes through a switch 11, is converted into a digital signal by an encoder 12, and is output from an output terminal 2 via a separation circuit 13. Output.

Conversely, the digital signal input to terminal 3 is connected to coupling circuit 1.
4, is converted into an analog signal by a decoder 15,
Unnecessary harmonic components are removed by the filter 17 via the switch 16 and output from the output terminal 4.

A sine wave digital monitoring signal generated by the monitoring signal generation circuit 18 and becoming a sine wave when demodulated is time-division multiplexed with the input digital signal in the coupling circuit 14, converted into an analog signal by the decoder 15, and then sent to the switch 16. is applied to the buffer circuit 19 by.

Buffer circuit 19 sends the output signal of decoder 15 to encoder 12 via switch 11 .

This supervisory signal digitized by encoder 12 is
The signal is applied to the monitoring signal receiving circuit 20 by the separation circuit 13 .

Here, the switches 11 and 16 determine the destinations of the input/output analog signals and analog supervisory signals processed in time division by the encoder 12 and decoder 15, respectively.

On the other hand, the separation circuit 13 and the combination circuit 14 switch and control the input/output signal and the monitoring signal in the form of digital signals, so that the encoder 12 and the decoder 15 can handle both signals alternately in a time-sharing manner.

The supervisory signal receiving circuit 20 again compares the amplitude of the digitized supervisory signal with the standard value, and outputs an alarm signal to the terminal 5 if the difference is greater than a predetermined value.

Such a monitoring system has drawbacks, such as the inability to monitor the operation of filters 10 and 17, and the fact that encoder 12 and decoder 15 must operate at twice the originally required operating speed.

Nowadays, the encoder 12 and decoder 15 can be realized on a single chip using LSI technology, and the filters 10 and 17 tend to be realized with active filters, so it is necessary to include the filters for system monitoring. It is necessary to monitor the operation of the circuit.

Further, the encoder and decoder made of IC are easier to implement and more economical as they operate at lower speeds, and consume less power.

Conventionally, an encoder and a decoder each have S SI (sm
al, 1=size integrated ci
Although it was relatively expensive, it was easy to increase the speed, so as in the example above, not only one signal but many analog and digital signals were processed in a time-sharing manner. It is meaningful to simply monitor the operation of only the encoder and decoder that are commonly used, and such a method has been commonly used in the past.

The object of the invention is to provide an encoder-decoder monitoring device which overcomes the above-mentioned drawbacks.

Another object of the present invention is to facilitate the integration of the encoder and decoder without speeding up the operation of the encoder and decoder, and to monitor even somewhat unreliable circuits such as active filters. The goal is to provide equipment.

That is, the monitoring device of the present invention includes an encoder that converts an analog signal into a digital signal, a decoder that converts the digital signal into an analog signal, means for applying a pulse-like digital signal to the decoder, and the decoder. The present invention is characterized in that it includes means for applying an output analog signal of the encoder to the encoder for a short time and means for analyzing the output digital signal of the encoder, and monitors the operation of the encoder and the decoder.

The present invention will now be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention.

In FIG. 2, reference number 1 is an analog signal input terminal;
Reference numeral 2 is a digital signal output terminal, reference numeral 3 is a digital signal input terminal, reference numeral 4 is an analog signal output terminal, reference numerals 10 and 17 are filters, reference numeral 12 is an encoder, reference numeral 15 is a decoder, Reference numeral 23 is a separation circuit, reference numeral 24 is a coupling circuit, reference numeral 25 is an impulse-like monitoring signal generator, reference numeral 26 is a monitoring signal receiving circuit, and reference numerals 21 and 22 are switches.

A digital signal corresponding to the impulse generated by the supervisory signal generator 25 is applied to the decoder 15 after temporarily blocking the input digital signal at the coupler 24 .

The monitoring signal demodulated by the decoder 15 and filter 17 is applied to the filter 10 through a path temporarily configured by switches 22 and 21.

At this time, the switch 21 temporarily blocks the input analog signal from the terminal 1.

The output of the filter 10 is fed to an encoder 121,
The supervisory signal encoded in step 2 is applied to the supervisory signal receiving circuit 26 by the separation circuit 23.

In this method, input analog signals and digital signals are momentarily interrupted by a switch 21 and a coupling circuit 24, and a path (monitoring signal generator 25 - coupling circuit 24 - decoupler 15 - Filter 17-switch 22-
Switch 21 - Filter 1 - Encoder 12 - Separation circuit 23
- Create a receiving circuit 26) and create a system.

A check is made.

When the analog signal is an audio signal, the cutoff frequency of the filters 10 and 17 is approximately 4 K) + z, and the sampling frequency is 8
Since it is 1 Glz, the input signal cutoff time only needs to be about 1 ms, and its transmission characteristics hardly deteriorate.

3 to 7 are circuit diagrams showing specific circuits of the switch 21, separation circuit 23, coupling circuit 24, switch 22, and supervisory signal receiving circuit 26 used in FIG. 2, and FIG. 9 is a circuit diagram showing these circuits. The waveform of the circuit control signal is shown.

These circuits will be briefly explained below.

The switch 21 shown in FIG. 3 has an analog signal input terminal 3□, a control signal input terminal 32, an external terminal 35 to which the output of the switch 22 in FIG. 2 is input, and a control input from the control terminal. The FETs 33, 3 . (field effect transistor) and an amplifier that amplifies the output of these FETs3. When the signal from the switch 22 is input to the external terminal, the FET 33
is turned off, temporarily blocking the analog signal, and FET3. is turned on.

The coupling circuit 24 shown in FIG. 4 includes a digital signal input terminal 4, a control input terminal 46, and a supervisory signal input terminal 4.
□, AND gates 44 and 4 that operate according to the control input signal from the control input terminal 4□, and the supervisory signal is input to the supervisory signal input terminal 4□, and the control signal (FIG.
) is input, the digital signal input from the terminal 41 is blocked and only the monitoring signal is output to the output terminal 43.

The separation circuit 23 shown in FIG. 5 includes an input terminal 5□ to which the output of the encoder 12 is input, a control input terminal 52, and an AND gate circuit 53 that operates according to signals from the control input terminal 5□. , 54, etc., and when a monitoring signal is input to the terminal 51 and a control signal (FIG. 9 4) is input, the gate circuit 5
3 is activated to separate the supervisory signal to output terminal 56.

Note that, when a monitoring signal is input to the input terminal 51, the voltage voltage Vcc input to the gate circuit 55 is input to the digital output terminal 5. This is to bring the level to rHJ.

The switch circuit 22 shown in FIG. 6 has a terminal 6□ to which an analog signal, which is the output of the filter 17, is input, a control input terminal 6□, and a switch circuit 22 that is turned on and off according to a control signal from the control input terminal. Including FET63゜64 to be turned off, terminal 6□
When a monitoring signal is input from the analog signal output terminal 6. and a control signal (FIG. 9, 2) is input, the FET 63 is turned off. The monitoring signal is not output to the switch 21, but is output to the monitoring signal output terminal connected to the input terminal of the switch 21.

The supervisory signal receiving circuit 26 shown in FIG. 7 includes a shift register 7□ in which a supervisory signal is stored, an AND gate 5□ that operates according to the output of this shift register 7□, and a supervisory output output. terminal 5.

The waveform of the monitoring signal to the receiving circuit 26 is as shown in FIG. 3, so the standard peak value of the monitoring signal is
ooolloJ, and the allowable range is ``1100000''.
0'' to 1100IIIJ, if the input monitoring signal deviates from the above-mentioned allowable range and becomes larger or smaller under the control of the control signal 5 (FIG. 9, 5),
The gate circuit 72 operates and outputs the level rLJ to the terminal 5.

The pulse width of the control signal input to the control signal input terminal 73 is synchronized with the clock signal from the clock terminal 74, so that, for example, only the upper 4 bits of the 8-bit monitoring signal are input to the shift register. It has been decided.

FIG. 9 is a diagram showing waveforms of control signals input to the control input terminals of the circuits shown in FIGS. 3 to 7.

As described above, according to the monitoring circuit according to the present invention, it is possible to monitor not only the encoder and decoder but also the filter, and it is also possible to monitor the encoder and decoder without increasing their speed. It can be performed.

In the embodiment shown in FIG. 2, the monitoring signal is an impulse signal, but it is not limited to this, and any signal that continues for a short period of time may be used.
Any pulsed signal can be used as a monitoring signal in this method.

Further, as a method of receiving a monitoring signal, it is possible not only to simply compare the input signal with a standard signal, but also to digitally process the input signal to make it easier to detect a failure.

For example, although the above method deals with the impulse response of a modulation/demodulation circuit including a filter, encoder, and decoder in the time domain, it is also possible to calculate the frequency response from the impulse response and compare it with a standard.

Further, although the system according to the present invention temporarily cuts off input signals, it is also possible to check whether there is a call using a line control signal and then perform this test without affecting the call in any way.

Furthermore, it is also possible to detect the presence or absence of an input/output signal by digital means without relying on line control signals, and to perform this test when there is no signal.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a conventional monitoring system, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 8 is a waveform diagram showing an impulse response of a modulation/demodulation circuit, and Figs. Specific circuit diagrams of the switches, coupling circuits, separation circuits, and supervisory signal receiving circuits shown in the blocks of Fig. 2, and Figs. 9 0 to 5 show the relationships between control signals and input digital signals used in these circuits. figure. 1 and 2, 1...analog input terminal, 2...digital output terminal, 3...
...Digital input terminal, 4...Analog output terminal, 10...Filter, 11...
Switch, 12... Analog-digital converter, 13... Separation circuit, 14... Combining circuit, 15... Digital-analog converter,
16...Switch, 17...Filter,
18...Monitoring signal generation circuit, 19...
Buffer circuit, 20... Monitoring signal receiving circuit, 21,
22...Switch, 23...Separation circuit, 24...Coupling circuit, 25...Monitoring signal generation circuit, 26...Monitoring signal This is a receiving circuit.

Claims (1)

[Claims] 1. An encoder that converts analog signals into digital signals, and a decoder that converts digital signals into analog signals.
means for applying a pulsed supervisory digital signal to the decoder; means for briefly applying an analog signal, which is the output of the decoder, to the encoder; and a supervisory digital signal, which is the output of the encoder. and means for analyzing the encoder-decoder monitoring apparatus.