JP2877890B2 - Channel board of PCM terminal equipment - Google Patents

Description

The present invention relates to a PCM terminal for converting an input signal in which an audio signal in an audio band and a data signal outside the audio band are superimposed into a PCM code and transmitting the PCM code. It relates to the channel board of the device.

[Prior art] Normally, in the PCM transmission method, an input signal of an audio band is 8 kHz.
Sampling at the sampling frequency of
PCM signals are encoded and then multiplexed for transmission.

By the way, data signals outside the voice band (frequency of 4 kHz or more) cannot be transmitted by the above method.

Conventionally, when transmitting an input signal in which an audio signal in the audio band and a data signal outside the audio band are superimposed using the PCM transmission method, sampling is performed at a sampling frequency of 8 kHz or more (at least twice the used bandwidth). , And encodes it into a PCM signal for transmission.

[Problems to be Solved by the Invention] However, in the conventional method of increasing the sampling frequency, as the sampling frequency increases, the amount of transmission data per unit time increases and the number of time slots increases, resulting in high-speed operation. There is a problem that the device of the above is required.

The present invention provides a channel board for a PCM terminal device that encodes and transmits an input signal in which an audio signal in an audio band and a data signal outside the audio band are superimposed into a PCM signal without using an expensive high-speed operation device. The purpose is to provide.

[Means for Solving the Problems] According to the present invention, an input signal in which an audio signal in an audio band and a data signal outside the audio band are superimposed is converted into a PCM code, and the PCM code is input to a demultiplexing circuit. A channel board of a PCM terminal device, comprising a codec circuit, a channel interface, a data detection circuit, first and second first-in first-out memories, and a data transmission circuit; Encoding only the audio signal from the signal, outputting an encoded audio signal to the channel interface, and decoding a received encoded audio signal from the channel interface, wherein the data detection circuit outputs the out-of-band data from the input signal. Signal, and converts the data contained in the out-of-band data signal into a binary signal to convert the data into a first signal. Write to a write-out memory, and the channel interface reads out the binary signal from the first first-in first-out memory at a predetermined timing into the coded audio signal from the codec, and Multiplexed and output to the separation multiplexing circuit as the PCM code, and separate the reception signal from the separation multiplexing circuit into a reception coded voice signal and a reception binary signal, and convert the reception coded voice signal into The received binary signal is output to an encoding / decoding circuit to the second first-in / first-out memory, and the data sending circuit reads out the stored contents of the second first-in / first-out memory, and outputs a modulated data signal. , A channel board of the PCM terminal device is obtained.

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

FIG. 1 shows a block diagram of one embodiment of the present invention. First
Referring to the figure, the channel board of the present embodiment includes a code / decode (CODE / CODEC) circuit 11, a data detection circuit 12, a first first-in first-out (FIFO) memory 1
3, channel interface (CH INF) circuit 14, second first-in first-out (FIFO) memory 1
5 and a data transmission circuit 16.

Next, the operation of this channel board will be described. First, the transmission operation will be described.

The input signal input to the input terminal 17 is divided into two parts, one of which is supplied to the CODEC circuit 11 and the other is supplied to the data detection circuit 12. Here, the input signal is a signal in which an audio signal in an audio band and a modulated data signal outside the audio band are superimposed.

The CODEC circuit 11 passes the input signal through a band-pass filter to remove the modulated data signal. then,
The input signal which is only the audio signal is sampled at a predetermined sampling frequency and encoded. here,
The sampling frequency is determined by the clock from the CH INF circuit 14.

The data detection circuit 12 detects a modulated data signal from the input signal and converts it into a binary signal. Then, the data signal converted into the binary signal is written to the FIFO memory 13.

The audio signal encoded by the CODEC circuit is supplied to the CH INF circuit 14 as an encoded audio signal. The CH INF circuit 14 reads a binary signal from the FIFO memory 13 at a predetermined clock, multiplexes the binary signal with a coded audio signal by bit stealing processing, and sends the multiplexed signal to the demultiplexer as a PCM code. This bit stealing is performed, for example, once every six frames.
The maximum data transmission rate at this time is 8/6 kbps.

The PCM code sent to the demultiplexing circuit is time-division multiplexed with the PCM code sent from another channel board (not shown) and transmitted to another station.

 Next, the receiving operation will be described.

The received time-division multiplexed PCM code is demultiplexed by a demultiplexing circuit on a channel basis to become a demultiplexed reception signal. This separated reception signal is further separated by the CH INF circuit 14 into a reception encoded voice signal and a reception binary signal.

The received encoded audio signal is input to the CODEC circuit 11, decoded, and output as an audio signal.

The received binary signal is written into the FIFO memory 15, and the data transmission circuit 16 reads out the contents of the FIFO memory 15 at a predetermined clock. The read content is output as a modulated data signal (out-of-band data signal).

Finally, the data signal output from the data transmission circuit is superimposed on the audio signal output from the CODEC circuit 11, and supplied to the output terminal 18 as a reception output.

According to the present invention, the audio signal and the out-of-band data signal included in the input signal are separately encoded and converted into a binary signal.
After that, the multiplexing allows the out-of-band data signal to be transmitted simultaneously with the voice signal by the PCM transmission method without using a high-speed operation device.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention. 11: CODEC circuit, 12: Data detection circuit, 13: First
FIFO memory, 14 ... CH INF circuit, 15 ... Second FIFO
Memory, 16 Data transmission circuit, 17 Input terminal, 18
... Output terminal.

Claims (1)

(57) [Claims] An input signal in which a voice signal in a voice band and a data signal outside the voice band are superimposed is converted into a PCM code,
In a channel board of a PCM terminal device for inputting the PCM code to the demultiplexing circuit, a code decoding circuit, a channel interface, a data detection circuit, first and second first-in first-out memories, and a data transmission circuit The code decoding circuit encodes only the audio signal from an input signal, outputs an encoded audio signal to the channel interface, and decodes a received encoded audio signal from the channel interface, the data detection circuit. Detects the out-of-band data signal from the input signal, converts data included in the out-of-band data signal into a binary signal, and writes the binary signal to the first first-in first-out memory. From the encoded audio signal from the 1 is read out from the first-in first-out memory at a predetermined timing, is multiplexed by bit steal, is output as the PCM code to the demultiplexing circuit, and a separated reception signal from the demultiplexing circuit is a received encoded voice signal. And the received binary signal, and outputs the received encoded voice signal to the codec circuit and the received binary signal to the second first-in first-out memory. 2. A channel board for a PCM terminal equipment, which reads out the stored contents of a second first-in first-out memory and outputs a modulated data signal.