JPS60169296A - Multi-frequency signal system for terminal device - Google Patents

Abstract

PURPOSE:To avoid malfunction due to a voice and noise by transmitting another frequency signal different from a multi-frequency signal at the same time when the multi-frequency signal is transmitted and allowing the reception side to recognize a correct multi-frequency signal based on the signals. CONSTITUTION:A signal of low group frequency, a signal of high frequency and a signal of 400Hz are transmitted from a telephone terminal device T. The signal of low group frequency is inputted to a detection circuit DET via a band pass filter BPF-L, limiter LIM(L) and band pass filters BPF(L1)-BPF (L4), converted into a DC component and the result is inputted to AND gates G1-G4. Similarly the signal of high group frequency is inputted to AND gates G5-G8. The frequency signal of 400Hz is inputted to the AND gates G1-G8 via a selection amplifier circuit 3F, a band pass filter BPF and a detection circuit DETa to open the AND gates G1-G8. Thus, only when the 400Hz signal exists, the multi-frequency signal is recognized.

Description

Detailed Description of the Invention (a) 9 Technical Field of the Invention The present invention relates to a multi-frequency signal system for terminals, and particularly to a multi-frequency signal system for terminals used between telephone terminals, between a telephone terminal and an exchange, etc. It is related to.

(b) Prior Art and Problems As is well known, a multi-frequency signal system is used for transmitting and receiving signals between telephone terminals, between telephone terminals and exchanges, etc. This multi-frequency signaling system uses four high frequencies belonging to the voice band and four
Prepare 1 low frequency, and 1 each from high and low image frequencies.
In this method, several frequencies are selected and transmitted simultaneously, and the receiving side discriminates the signal based on the combination of these frequencies.

FIG. 1 is a block diagram showing an example of a conventional multi-frequency signal system for terminals.

In the figure, T is a telephone terminal, BEF-L is a hand-eliminate filter that blocks the low frequency band, BEF-H is a band-eliminate filter that blocks the high frequency band, L IM (L), t, IM (H) is a limiter circuit, BPF is a bandpass filter, DET is a detection circuit, L1 to L4 are signals of a low group frequency, and H1 to H4 are signals of a high group frequency, respectively. Note that BPF (LL) represents a band pass filter that passes only the signal L1 of the low group frequency.

FIG. 2 is a diagram showing the characteristics of band eliminate filters BEF-L (indicated by dotted lines) and BEF-H (indicated by solid lines) used in the conventional multi-frequency signal system for terminals.

The details of reception in the conventional multi-frequency signal system for terminals will be explained below with reference to the figures.

Assume that a low frequency signal L2 and a high frequency signal H3 are selected and sent from the telephone terminal T.

The low group frequency signal L2 is passed through the hand eliminate filter B.
Pass through E F -H and enter the limiter circuit LIM (L)
to go into. At this time, the high group frequency signal H3 is blocked by the panned elimination filter BEF-,H. Next, the low group frequency signal L2 undergoes amplitude control by the limiter circuit LIM (L), passes through the low group frequency band pass filter BPF (L2), and is converted into a DC component by the detection circuit DET.

The high group frequency signal H3 is passed through band eliminate filter B.
It passes through EF-L and enters the limiter circuit LIM(H).

At this time, the low group frequency signal L2 is blocked by the band eliminate filter BEF-L. Next, the high group frequency signal H3 is subjected to amplitude control by the limiter circuit LIM (H), and the high group frequency hand pass filter BPF (H3
) and is converted into a DC component by the detection circuit DET.

In this way, each signal is converted into a DC component, and the content of the signal is determined based on this.

However, when noise enters the multi-frequency signal, the amplitude of the signal wave component output from the limiter circuit LIM decreases as the noise increases, resulting in a disadvantage that it cannot be received.

Furthermore, the multi-frequency signal system is established under the condition that the multi-frequency signal and the audio signal do not coexist, and has the disadvantage that malfunctions may occur if the audio signal is mixed in by mistake.

(C)0Object of the invention The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art,
It is an object of the present invention to provide a multi-frequency signal system for terminals that does not malfunction due to voice or noise.

(d) 9 Structure of the Invention According to the present invention, in a multi-frequency signal transmission/reception system consisting of high group and low group frequencies, when the multi-frequency signal is transmitted from the transmitting terminal side, the multi-frequency signal is For a terminal, characterized in that a frequency signal and another frequency signal different from the frequency signal are simultaneously transmitted, and a receiving side recognizes only the received multi-frequency signal when receiving the different frequency signal as the correct multi-frequency signal. This is achieved by providing multi-frequency signaling.

Further, in the multi-frequency signal system for terminals as set forth in claim 1, a circuit is provided for selectively receiving frequency components around 3KIIz, and the multi-frequency signal received when the circuit has an output is treated as an erroneous signal. This is achieved by providing a multi-frequency signaling system for terminals that is characterized by rejection.

(e) 1 Embodiment of the Invention FIG. 3 is a block diagram showing an embodiment of the multi-frequency signal system for terminals according to the present invention.

In the figure, OSC is a 400 Hz oscillator, CON is a coupling circuit, BPF-L is a band pass filter that passes low group frequencies, BPF-H is a band pass filter that passes high group frequencies, and 3F is a frequency component of about 3 KHz. A circuit that has a function of selectively amplifying B P F '<400
Hz) is 400) A bandpass filter that passes only the 1z component, DETa is a detection circuit, and 01 to G8 are AND gate circuits.

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

In the present invention, when transmitting a multi-frequency signal on the transmitting side, a frequency of 40011z is simultaneously transmitted.

Assume that the telephone terminal T now sends a signal L2 of a low group frequency, a signal H3 of a high group frequency, and a signal of 40011z.

71Y frequency signal L2 is passed through bandpass filter B1)
It passes through F-L, enters the limiter circuit LIM(L), and receives the amplitude side fffll. Next, it passes through a low group frequency band pass filter BPF (L2) to the detection circuit DE.
It is converted into a DC component at T, and its output is input to the AND gate circuit G2.

The high group frequency signal H3 is filtered by bandpass filter BEF-H.
The signal passes through the limiter circuit LIM(H) and is subjected to amplitude control. Next, the high group frequency band pass filter BPF
(H3) and is converted into a DC component by the detection circuit DET, and its output is input to the AND gate circuit G7.

The signal with a frequency of 400 Hz passes through the circuit 3F, the band pass filter BPF (400 Hz), enters the detection circuit DETa, and is converted into a DC component, and this DC component opens the AND gate circuits 01 to G8.

Therefore, outputs are generated in the AND gate circuits G2 and G7. Note that when there is no DC component output from the detection circuit DETa, the AND gate circuits 61 to G8 are inhibited.

By sending out a 400 Hz frequency signal at the same time as a multi-frequency signal like this, the receiving side can recognize that a multi-frequency signal exists when there is a 400 Hz signal, thereby preventing malfunctions. .

Also, in the multi-frequency signal system, the multi-frequency signal and the audio signal do not arrive at the same time, so when the audio signal comes in, the probability is 3.
KI (noting that there are many frequency components near z, 400
For fiz, the input is output on its side, but 3KI (
Using circuit 3F, which has the function of selectively amplifying and detecting frequency components around z, if there is an output from this circuit, it is determined that audio signals are mixed, and the 400 Hz signal is cut off and an AND gate is applied. Since circuits 01 to G8 are inhibited, malfunctions can be prevented.

On the other hand, when a multifrequency signal and noise are input at the same time, components outside the multifrequency signal band are removed by bandpass filters BPF-L and BPF-H, so the limiter circuit LI
It is possible to suppress a decrease in the signal component of M. As a result, poor reception of multi-frequency signals due to noise is improved.

(f) 1. Effects of the Invention and More EF As described in detail, the present invention has the great effect of realizing a multi-frequency signal system for terminals that does not malfunction due to voice or noise.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional multi-frequency signal system for terminals. Figure 2 shows band eliminate filters BEF-L and B used in the conventional multi-frequency signal system for terminals.
It is a figure showing the characteristic of EF-H. FIG. 3 is a block diagram showing an embodiment of the multi-frequency signal system for terminals according to the present invention. In the figure, T is a telephone terminal, BEF-L is a band eliminate filter that blocks low frequency bands, BEF-H is a band eliminate filter that blocks high frequency bands, and L
IM (L) and L IM (H) are respectively limiter circuits, BPF is a band pass filter, DET is a detection circuit,
L1 to L4 are low group frequency signals, H1 to H4 are high group frequency signals, OSC is a 40011z oscillator, C
ON is a coupling circuit, BPF-L is a band pass filter that passes a low group frequency, BPF-H is a band pass filter that passes a high group frequency, 3F is a circuit that has a function of selectively amplifying a frequency component of about 3 KHz, BPF (4
0011z) is a bandpass filter that passes only the 400 Hz component, DETa is a detection circuit, and 01 to G8 are AND gate circuits. Kaya 1 Illustration 2 Mouth

Claims (1)

[Claims] 1. In a multi-frequency signal transmission/reception system consisting of high group and low group frequencies, when the multi-frequency signal is transmitted from the transmitting terminal side, another frequency signal different from the multi-frequency signal is transmitted. A multi-frequency signal system for a terminal, characterized in that the multi-frequency signals are transmitted simultaneously, and on the receiving side, only the multi-frequency signal received when the other frequency signal is received is recognized as the correct multi-frequency signal. 2. In a multi-frequency signal transmission/reception system consisting of high group and low group frequencies, a circuit is provided to selectively receive frequency components around 3 KHz, and the multi-frequency signal received when the circuit has an output is an erroneous signal. A multi-frequency signal system for terminals that is characterized by rejecting as follows.