JPH0575298B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a method of half-duplex communication between stations,
The present invention relates to a data switching circuit required in a digital communication system using a code/decoding circuit such as CVSD (continuously variable slope delta modulation).

[Conventional technology]

FIG. 3 is a block diagram showing the configuration of a conventional data switching circuit. In FIG. 3, 50 is an input terminal for audio data coming from the other station, 52 is an input terminal for silent data generated within the own station, 54 is an output terminal, and 56 is an input terminal for audio data input from the input terminal 50 of n bits or more. A silence detection section 58 is a switch for switching between audio data and silence data.

Next, the operation of the conventional data switching circuit will be described. When communicating in half-duplex between stations using a code/decoding circuit such as CVSD, the transmission path:
When there is no sound, the level is kept at "0", and when there is sound, the audio signal (analog signal) is transmitted in a burst form. In such a communication system, when there is no sound, silent data in the pattern "1010..." is required as input. For this reason, when the transmission path is in a silent state, that is, "0" (level) is continuous in the receiving section, this is detected and the silent data of the "1010..." pattern is input to a coding/decoding circuit such as CVSD. There is a need.

Therefore, when the transmission path is silent, the silence detection unit 56 detects the silence state, the switch 58 switches from the audio data input terminal 50 to the silence data input terminal 52, and outputs the data to the output terminal 54. .

FIG. 4 is a timing chart of operations in the data switching circuit of FIG. In FIG. 4, 60 is input audio data, and 60-
a is a silent part, and 60-b is a sound part. 62
is the silent data of the “1010…” pattern. 66
is the output signal of the silence detector 56, which is the switch 58.
66-a is the "L" switching signal, and 66-b is the "H" switching signal. 64 is an output signal switched by the switch 58, 64-a is silent data of the "1010..." pattern, 64-b is sound data, and 64-c is silent sound data.

First, the silence detection section 56 detects continuous "0" at the audio data input terminal 50 and outputs the "L" switching signal 66-a as the switching signal 66.
As a result, the switch 58 selects and outputs the silent data 62 of the "1010..." pattern. Furthermore, when the sound part 60-b of the audio data 60 is input, the silence detection unit 56 outputs an "H" switching signal 66-b as the switching signal 66. Based on this output, the switch 58 selects and outputs the audio data 60.

Next, when the sound portion 60-b of the audio data 60 input from the audio data input terminal 50 changes to a silent portion 60-a, the silence detection unit 56 detects n
The time to detect consecutive “0” bits, that is, the silent state detection time 67 (silent audio data 64-c
(corresponding to the above), the switching signal 66 is changed to the "L" switching signal 66-a with a delay, and the switch 58 is switched to the silent data input terminal 52 side. The bit length n for detecting consecutive "0"s is determined by the code/decoding circuit such as CVSD and the system used.

[Problem that the invention seeks to solve]

In the conventional data switching circuit as described above, when the input audio data 60 changes from the sound part 60-b to the silent part 60-a, or depending on the system, from the silent part 60-a to the sound part 60-a, -b, a series of n bits of "0" of the silent audio data 64-c is output as the output signal 64 switched by the switch 58, so this output is used for encoding and decoding such as CVSD. When it is input to a circuit, it is demodulated as an output of an analog signal with the maximum amplitude, resulting in a problem that a large noise is generated.

The present invention was made to solve this problem, and uses a simple circuit configuration to perform data switching that does not output a series of n bits of "0" of silent audio data as an output signal due to data switching. The purpose is to obtain a circuit.

[Means for solving problems]

The data switching circuit according to the present invention includes a delay section that delays the audio data by n bits to the audio data input terminal, a silence detection section that detects a continuous silence state of n bits or more in the audio data, and a delay section. By using two detection units, including a voice detection unit that detects the presence of voice in delayed voice data, switching between voice data and silent data of the "1010" pattern is possible.

[Effect]

The data switching circuit of the present invention includes a hot water sound detection section that detects a silent state of n bits or more of sound data, and a sound detection section that detects sound presence of delayed sound data using a delay section that delays the sound data by n bits. A loud noise is generated by adding a section and controlling the switch using each silence detection signal and sound detection signal, which are switching signals output from the two silence detection sections and the sound detection section. This makes it possible to switch between audio data and silent data in the "1010" pattern.

〔Example〕

FIG. 1 is a block diagram showing the configuration of a data switching circuit which is an embodiment of the present invention. In FIG. 1, 10 is an input terminal for audio data, 12 is an input terminal for silent data with a "1010..." pattern, 1
4 is an output terminal; 16 is a delay unit that delays the audio data by n bits; 18 is a sound detection unit that detects the beginning of a sound in the delayed audio data delayed by the delay unit 16; A silence detection unit 22 detects a continuous silence state, and a silence detection unit 22 is a combination of a sound detection signal output from the sound detection unit 18 and the silence detection unit 2.
This is a switch that switches between audio data and "1010" pattern silence data based on the silence detection signal output from 0.

FIG. 2 is a timing chart of operations in the data switching circuit of FIG. 1. In FIG. 2, 30 is input audio data, and 30-
30-b is a silent part where a is a continuous "0" and a sound part. 32 is silent data of the "1010..." pattern. 36 is the output of the delay unit 16, which is delayed audio data of n bits, which is the same as the delay caused by n bits of consecutive “0” in the silence detection unit 20, and 36-
36-b is a silent part where a is a continuous "0" and a sound part. Reference numeral 38 denotes a voice presence detection signal, which is a voice detection output of the delayed audio data 36, 38-a is an "L" voice presence detection signal, and 38-b is an "H" voice presence detection signal. Reference numeral 40 denotes a silence detection signal, which detects whether there is a sound or not by predicting a delay of n bits required for detecting silence. Here, 40-a is an "H" silence detection signal, and 40-b is an "L" silence detection signal. 34 is Suitsuta 22
is the output signal switched by 34-
a is silent data with “1010…” pattern, 34-b
is the voice data with sound.

Next, the operation of the data switching circuit which is one embodiment of the present invention will be described. Sound detection unit 1
8 is in a silent state at first, so the sound detection signal 3
8, the "L" sound detection signal 38-a is output. Here, when the voice data 30 is input, the voice presence detection unit 18 outputs the “H” voice presence detection signal 38 - b as the voice presence detection signal 38 . The rise of this output can be used to create a sound detection timing. The silence detection signal 40 of the silence detection section 20 detects whether there is a sound or not by predicting a delay of n bits required for detecting silence. Since silence is detected by counting consecutive n bits of "0", there is actually a delay of n bits from the point where there is sound to silence. That is,
The time when silence in the undelayed audio data 30 is detected coincides with the time when the delayed audio data 36 becomes silent. This is because the delay unit 16 delays the above n bits. In this way, it is possible to detect silence in the delayed audio data 36, and at this time, the silence detection section 20 outputs the "H" silence detection signal 40-a as the silence detection signal 40. In this way, by controlling the switch 22 using the two sound detection signals 38 and the silence detection signal 40, n bits of "0", which is the silent sound data 64-c in the circuit of the conventional example, are controlled. It is possible to switch and output audio data and silent data of the "1010" pattern to the output terminal 14 without outputting continuous data. Therefore, an analog signal with the maximum amplitude is not generated, and as a result, data switching can be performed smoothly without generating noise.

In the above embodiment, the case of half-duplex communication has been described, but it can also be used for full-duplex communication, unidirectional communication, etc., and the modulation method is not limited to CVSD.

Furthermore, in the above embodiment, the silent state of the transmission line is a series of "0" levels, but depending on the system, it may be at other levels, and similarly, the silent data can also be a "1010..." pattern. It doesn't have to be, and it doesn't necessarily have to be created within your own station.

Further, in the above embodiment, the sound detection signal 38 and the silence detection signal 40 are used as signals for switching and controlling the switch 22, but the signal is not necessarily limited to these two signals. Various uses of these signals can be considered, such as logical operations and flip-flop set/reset.

〔Effect of the invention〕

As explained above, the present invention includes a data switching circuit in which a delay section for delaying the audio data by n bits is added to the audio data input terminal, and a silence detecting section for detecting a continuous silence state of n bits or more in the audio data. , by using two detection units, a voice detection unit that detects the presence of voice data delayed by the delay unit, it is possible to switch between voice data and silent data of the “1010” pattern, so a complicated circuit configuration is required. It can be constructed at low cost without any noise, and has the excellent effect of smoothly switching between audio data and silent data of the "1010" pattern without generating a large noise.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a data switching circuit which is an embodiment of the present invention, and FIG.
FIG. 3 is a block diagram showing the configuration of a conventional data switching circuit, and FIG. 4 is a timing chart of operations in the data switching circuit shown in FIG. In the figure, 10, 50... input terminal for audio data, 12, 52... input terminal for silent data, 1
4, 54...output terminal, 16...delay section, 18...
... Sound detection unit, 20, 56 ... Silence detection unit, 2
2,58...Switch, 30,60...Audio data, 30-a...Silent part of audio data 30, 3
0-b...Sound part of audio data 30, 32,6
2... Silent data, 34, 64... Output signal, 3
4-a... Silent data, 34-b... Sound data, 36... Delayed audio data, 36-a...
Silent portion of delayed audio data 36, 36-b...Speech portion of delayed audio data 36, 38...Sound detection signal, 38-a..."L" sound detection signal, 38-
b..."H" sound detection signal, 40...silence detection signal, 40-a..."H" silence detection signal, 40-b
..."L" silence detection signal, 60-a...silence part of audio data 60, 60-b...audio data 60
Sound part, 64-a...Soundless data, 64-b
...Sound audio data, 64-c...Soundless audio data, 66...Switching signal, 66-a...
"L" switching signal, 66-b... "H" switching signal. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1 As input data to the delta modulation decoder,
In a data switching circuit that switches to input audio data when there is a sound and input silence data in a "1010" pattern when there is no sound, there is a silence detection section that detects a continuous silence state of n bits or more, and a silence detection section that detects a continuous silence state of n bits or more. a delay section that delays the bit;
A voice detecting section detects the presence of voice of the delayed voice data delayed by the delay section, and is controlled by the output signal of the silence detecting section and the output signal of the voice detecting section, and the delayed voice data and the "1010" 1. A data switching circuit comprising a switch for switching between pattern data and silent data.