SU1695520A2 - Device for finding breaks in telephonic signal - Google Patents

Abstract

The invention relates to communication technology. The purpose of the invention is to improve the detection accuracy in the background noise. The device for detecting pauses in a telephone signal contains amplifier 1, rectifiers 2 and 9, threshold blocks 3, b and 12, el-IT 4, registration block 5, differentiation blocks 7 and 11, band-pass filter 8, logarithmic amplifier 10 , controlled rectifier 14, ADC 15, key 16, memory block 17, DAC 18, threshold level shaping unit 19, OR 21 and El BAN 21. The goal is achieved by providing an adaptive change in the threshold level, which is set above the channel noise level. 1 il.

Description

The invention relates to communication technology, can be used in interpolation systems and is complementary to ed. St. No. 1143295.

The purpose of the invention is to improve the accuracy of detection against interference by adaptive changes in the threshold level.

The drawing shows a structural electrical diagram of a device for detecting pauses in a telephone signal.

A device for detecting pauses in a telephone signal contains an amplifier 1, a rectifier 2, a first threshold block 3, an And 4 element, a registration block 5, a second threshold block 6, a differentiation block 7, a bandpass filter 8, an additional rectifier 9, a logarithmic amplifier 10, an additional block Differentiation 11, additional threshold block 12, additional logarithmic amplifier 13, controlled rectifier 14, analog-to-digital converter 15, key 16, memory block 17, digital-to-analog converter 18, block 19 ha, element OR 20, element BAN 21.

A device for detecting pauses in a telephone signal operates as follows.

The speech signal from the output of the telephone unit is supplied to amplifier 1, the output of which is supplied to rectifier 2 and bandpass filter 8. In the channel, consisting of series-connected rectifier 2 and threshold unit 3, the signal is evaluated at the absolute level, from the output of rectifier 2, the signal is received into a channel consisting of a logarithmic amplifier 13 connected in series, a differentiation unit 7, and a threshold unit 6. In this channel, a signal is evaluated according to its derivative over the entire band of the telephone channel. The derivative of the high-frequency component of the signal is estimated in another channel, consisting of a series-connected bandpass filter 8, an additional rectifier 9, a logarithmic amplifier 10, an additional differentiation unit 11 and an additional threshold block 12.

The detection threshold in the Trigger unit 6 is formed using an additional channel for analyzing the noise level, consisting of a serially connected controlled rectifier 14. An analog-to-digital converter 15, a key 16, a memory block 17, a digital-to-analog converter, and a block 19, while the input of the controlled rectifier 14 is connected to amplifier output 1.

In the absence of an information signal at the input of the device, a noise envelope is extracted in this channel, accumulated with a time constant of the order of 1 s, and, based on the rms value of the noise, a low level potential is established at the output of the threshold level generating unit 19. Key 16 is open.

When speech signals appear at the output of the OR element 20, an impulse arises that is allocated in one of the signal detection channels along its derivative (at the outputs of threshold blocks 6 and 12). From this pulse, a blocking pulse equal to the duration of the speech signal (of the order of 150 ms) is formed in the element PROHIBIT 21. The blocking pulse locks the key 16 and switches the accumulation time (ΐ _Η ®1 s) in the controlled rectifier 14, which does not allow to accumulate the level of the speech signal in the channel for analyzing the noise level. Thus, in the block 17 of the memory information is stored about the average noise level in the pause of the speech signal. The incoming speech signal is compared in absolute level with a remembered threshold, which can vary from a minimum to a maximum value. The minimum threshold is adaptive and is set above the noise level in the channel. The comparison result in the threshold block 3 is fed to the input of the element And 4 and then on. block 5 registration.

Claims (1)

Claim A device for detecting pauses in a telephone signal by bus. St. No. 1143295, characterized in that, in order to improve the detection accuracy against the background of noise by adaptively changing the threshold level, a sequentially connected controlled rectifier, an analog-to-digital converter, a key, a memory unit, a digital-analog converter and a threshold level shaping unit, as well as serially connected the OR element and the BANGE element, the output of which is connected to the control inputs of the key and the controlled rectifier, whose input is connected to the output of the amplifier, the output of the threshold level generation unit with It is connected with an additional input of the first threshold block, and the inputs of the OR element are output from the second threshold block, and an additional threshold block, respectively.