JPH01123540A - Voice data multiple transmitting device - Google Patents

Abstract

PURPOSE:To prevent a quantizing noise from appearing to a receiving output by sending a zero signal when a signal given to the output side of a filter to extract a sound signal is a prescribed level or below and sending a given signal as it does when the signal exceeds the prescribed level. CONSTITUTION:Both positive and negative clipping levels +Le and -Le for the level of an input signal IN are set to a center clipper circuit (CCP) 14, and when the level of the input signal IN is lower than this, the zero signal is sent as an output signal OUT, and when the level of the input signal IN exceeds this, the same signal IN is sent as the output signal OUT as it is. Consequently, when a clipping level + or -Le is set to a value a little higher than a noise level occurred by the quantizing of the data signal and the quantizing noise of the data signal passes through a band removing filter (BPF) 7, the noise does not arrive at the clipping level + or -Le of a CCP 14 and the CCP 14 sends the zero signal. Thus, the quantizing noise does not appear at a voice terminal 1 through a hybrid circuit (HYB) 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention multiplexes audio frequency bands by frequency division,
The present invention relates to a device that transmits audio signals and data signals over the same line.

[Conventional technology]

FIG. 3 is a block diagram, and FIG. 4 is a diagram showing the frequency characteristics of the p-wave device. In FIG. Line conversion is performed, and the signal is sent as a transmission audio signal to a band-removal F-wave unit (hereinafter referred to as nr:r) 3, where the frequency component of 1.4 to 2.1 KHz is suppressed using the characteristic V shown in FIG. The signal is applied to the HYB 5 via the coupler 4, and after 4-wire to 2-wire conversion is performed by the HYB 5, it is transmitted from the line terminal 6 to the transmission line.

Further, the received audio signal given to the line terminal 6 via the transmission line is separated from the transmitted audio signal by H115, and the BE
After only the frequency components of the audio signal are extracted in REFT similar to r3, the signal is subjected to 4-wire 2-wire conversion via HYB2 and then sent out from audio terminal 1.

On the other hand, the transmission data signal applied to the transmission data terminal 8 modulates a carrier wave in a modulator (hereinafter referred to as MOD) 9,
Bandpass filter (hereinafter referred to as BPF) with 1G! 7 As shown in the characteristics in Fig. 4, the data signal uses the frequency band 1.6 to 1.9 K) sent to.

Furthermore, the data signal of the modulated wave that arrived at the line terminal 6 via the transmission line is separated from the transmitted signal by the HYB5, and the BP
Similar to FIO, only the frequency components of the data signal are extracted by PFl 1, and then the demodulator (hereinafter referred to as DIM) 12
The received data signal is demodulated at the receiving data terminal 13 and sent out from the receiving data terminal 13 as a received data signal.

Therefore, in Figure 4, BBr3.7 and BPF'IQ
, 110 to show the loss characteristics for the frequency f,
In the example, in the audio frequency band of 0.3 to 3-4 KHz, 1
．． Frequencies excluding 4-2.1 KHz and 1.6-1.9K
Audio signals and data signals are multiplexed by frequency division using a frequency of Hz, and are transmitted and received using the same circuit.

[Problem that the invention seeks to solve]

However, when a PCM line is used as a transmission line, quantization noise occurs and degrades the voice-to-noise ratio S/N11.Although it does not cause any particular problem when a voice signal is present, When there is only a data signal with no signal, quantization noise caused by quantization of the data signal leaks into the audio signal band, and since the audio signal is no signal, the leaked quantization noise dominates 8/Nq. This has created a problem that is getting much worse.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention is constructed by the following means.

That is, in the receiving section of the multiplex transmission device mentioned earlier, a zero signal is sent to the output side of the filter that extracts the audio signal when the applied signal is below a predetermined level, and when the signal exceeds a predetermined level, a zero signal is sent to the output side of the filter that extracts the audio signal. It is equipped with a center clipper circuit that sends out the applied signal as it is when the signal is received.

[Effect]

Therefore, when the level of the audio signal decreases and there is no signal, the center clipper circuit sends out a zero signal when the level is below a predetermined level. When exists,
This signal is transmitted as is and passes through without causing any problem in receiving the audio signal.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to FIGS. 1 and 2 showing embodiments.

Fig. 1 is a block diagram of the main parts of the receiving section mainly consisting of BBr2 and BPFl 1 in Fig. 3, and Fig. 2 is a diagram showing the input/output characteristics of the center clipper circuit (hereinafter referred to as CCP). In this system, a CCP 14 is provided on the output side of the BBr2 that extracts the audio signal, and the received audio signal is sent to the HYB 2 via this.

In this case, C'cP14 is set with both positive and negative clipping levels +Le and -Lc with respect to the level of the input signal IN, as shown in Fig. 2, and when the level of the input signal IN is below this level, the output signal is A zero signal is sent out as OUT, and when the level of the input signal IN exceeds this level, the same signal IN is sent out as is as the output signal OUT.

Therefore, if the clipping level ±Lc is set to a value slightly higher than the noise level caused by the quantization of the data signal, even if the quantization noise of the data signal passes through BBr2, it will not reach the clipping level ±Le of the CCP14. CCP14 will send out a zero signal, and HY
No quantization noise appears at the audio terminal 1 via B2.

Also, when a received audio signal exists, its level exceeds the clipping level ±Le, so the received audio signal passes through CCP14 as it is, and HYB -2
The quantization noise between the audio signal and the audio terminal 1 is masked by the received audio signal, and does not pose any particular problem in reception.

Note that the quantization noise when only the data signal exists is
The level of the data signal is defined, and the rounding that can be easily predicted based on this may be used, and the clipping level ±Le may be determined accordingly, and a known CCP 14 may be used.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a CCP is provided on the output side of the audio signal extraction filter of the receiving section, thereby blocking quantization noise.
With the simple configuration of just adding CP, quantization noise when using a PCM line does not appear in the reception output, and the S/Nq when only data signals are present is greatly improved.
Remarkable effects can be obtained in frequency-division multiplexed voice/data transmission using a CM line.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a block diagram of the main part, FIG. 2 is a diagram showing the input/output characteristics of the center clipper circuit, and FIGS. 3 and 4 are conventional An example is shown in Figure 3, which is a block diagram. FIG. 4 is a diagram showing the frequency characteristics of the F-wave device. 1...Audio terminal, 2.5...Hybrid circuit, 6...Line terminal, T...O band removal filter, 1
411111 center clipper circuit,! N...Input signal, 0UT--"/Output signal, +Le, -Le
... Clipping level. Figure 1 Figure 2

Claims (1)

[Claims] In the receiving section of a device that multiplexes the audio frequency band by frequency division and transmits the audio signal and the data signal over the same line, the signal applied to the output side of the filter that extracts the audio signal is below a predetermined level. 1. A voice/data multiplex transmission device comprising a center clipper circuit which transmits a zero signal when the signal exceeds the predetermined level and transmits the applied signal as is.