JPS61111026A - Side tone preventing circuit of wireless telephone set - Google Patents

Abstract

PURPOSE:To obtain optimum side tone preventing effect by switching plural balancing circuits provided to a master set side with the operation from a slave set side. CONSTITUTION:When a switch 4 is turned on at the slave set side, an AND gate 5 is opened, a rectangular wave with a proper period is fed to a gate control circuit 2 to generate a pulse signal and the signal is superimposed on a transmission voice signal and the result is transmitted to the master set side. The said pulse is detected at the master set side, inputted to a counter 13 as a pulse (d) and counted. When the counter 13 counts a prescribed number, the Q output of the counter 13 goes to a high level, an AND gate 12 is closed to stop count. The counter 13 is reset at a prescribed period and then the Q output (f) at that point of time is read in a D FF15. An output of the FF15 rises only once corresponding to one operation of the switch 4, the number of leadings is counted by a counter 16, and balancing circuit 22 are selected sequentially in response to the count by a multiplexer 17. Thus, an optimum balancing circuit is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a side sound protection circuit in a wireless telephone device.

In conventional telephone equipment, a sidetone prevention circuit for reducing the sidetone phenomenon in which a transmission signal transmitted from a transmitter returns to the receiver side is well known (for example, 58-10693). In order to reduce the side volume (sidetone balance) in such a side sound prevention circuit, it is necessary to perform impedance matching between the balance circuit that constitutes the side sound prevention circuit and the telephone line. However, the line impedance of a telephone line varies depending on the line diameter and distance. Therefore, a configuration is known in which multiple balanced circuits are provided, and the balanced circuit that minimizes the side volume is selected by operating nine selector switches on the main body of the telephone device (for example, the above-mentioned patent application Showa 58-1069
(See the right column of page 1 of No. 36).

C. Problems to be Solved by the Invention In a wireless telephone device consisting of a base unit connected to a telephone line and a slave unit connected to the base unit via wireless communication, The system is designed to enable switching of a plurality of balance circuits by operating the handset from the handset side.

2. Measures to solve the problem: A switch for the slave unit and a circuit that generates a pulse signal in response to the operation of this switch is installed, and a pulse signal sent from the slave unit is provided for the master unit. A counter for counting, a plurality of balance circuits, and a selection control circuit for selectively controlling the balance circuit in response to the output of the counter are provided.

E. Operation When a switch is operated on the slave unit, a pulse signal is sent to the master unit in response.

On the base unit side, this pulse-like signal is counted by a counter, and one balanced circuit is selected from a plurality of balanced circuits by the output of a selection control circuit driven in response to the output of this counter. Ru. The user repeats the switch operation until the optimum side sound protection effect is obtained.

The pilot signal output from the embodiment pilot signal generation circuit m is input to the gate control circuit (2).

The pilot signal is also input to a frequency divider (3) K, and a rectangular wave for gate control (see FIG. 3(b)) is created. The period (T1) of this rectangular wave is several mBe08 degrees.

When the switch (4) is turned on, [”ff13
1'9(a) de.

Reference], Ann. The gate (5) is opened and a square wave is applied to the gate control circuit (2) (which may e.g. consist of a multiplexer, analog switch, etc.), thus causing the
) A pulse-like signal as shown in K is created. Is this pulse-like signal the same as the transmitting audio signal? Is this a composite image? 3tl) K is applied and combined, and further subjected to, for example, FM modulation in a modulation circuit (7) and transmitted to the base unit side. That is, the pulse-like signal for switching the balance circuit is transmitted to the base unit side in a form in which the sum of the transmitted voice signals is superimposed.

The signal received on the base unit side is sent to the demodulation circuit (8)
PM demodulation is performed, and a pilot signal frequency component is extracted by a bandpass filter (9). The output of the bandpass filter (9) is connected to the detection circuit (field) and the comparator (11).
), and the comparator (11) outputs a pulse as shown in FIG. 3 (, L). This pulse (a) is input to the counter via the anti-game (16) and counted. When the counter Ql counts a predetermined number (for example, several tens), the q output of the counter (11) becomes high level, and the following Since the output of the inverter (14) becomes low level, the AND gate a is closed and subsequent counting is stopped.The counter Q1 has a constant period (T2) K
The current Q output (f) of counter 01 is read into the D-type flip-prop Q@. A reset signal (-) is output from the reset signal generation circuit (21), and this signal (e) can be created by frequency-dividing the clock output from the clock generation circuit 4. Compared to the read timing to flip-flop 01, the reset timing of counter (11) is determined by the delay circuit -
Since the output is slightly slower, reading data using the flip-flop (1-) becomes reliable.

In response to one operation of the switch (4), the output of the flip-flop (see Fig. 3(g)) rises only once, and the number of rises (i.e., the number of times the switch (4) is turned on) rises only once. The number of operations] is counted by a counter aQ, and the multiplexer H then selects a balanced circuit (2'A) corresponding to the count value of the counter (lφ, that is, flip-prop Q~, The counter α→ and the multiplexer (17+ constitute a selection control circuit (I). In this way, each time the switch (4) is operated, the balance circuit (22-
1, 22-2, =-・22-T11) are sequentially selected, and an optimal balanced circuit can be selected. Note that after the balanced circuit (22-m) is selected, the balanced circuit (22-m) is selected again.
1) is selected cyclically.

Now, the gate control signal (b) (i.e., the pulsed signal (C
The reason why the period (T1) of )) is set to several msec is as follows.
It is as follows. The pilot signal is also used to close the telephone line and send out dial pulses. When sending out dial pulses, the pilot signal is about 50
~l QQ! It will be gated for 86C [see Figure 3 (color)]. Then, on the main unit side, PLI
, (phase locked loop) (23) detects this, and this detection output [see Figure 3 (1)] K is used to connect the line closing relay (23).
By turning 4J on and off, a dial pulse is sent to the telephone line. PLL1f by pulse-like signal (C)
The period (T
1) is selected to be sufficiently smaller than the period of the dial pulse.

In addition, the counter (llIri) is configured to count an appropriately large value (for example, several tens) and set its Q output to a high level when it reaches 9, but it malfunctions due to noise [see Figure 3 (a')]. This is to prevent the noise from being mistaken for the operation of switch (4).

The reset cycle (T2) of the counter ^1 is, of course, set to a value shorter than the on-operation period of the switch]4).

According to the present invention described above, optimal sidetone characteristics can be obtained even in a wireless telephone device.

[Brief explanation of the drawing]

The drawings all show a wireless telephone device 1 according to the present invention.
Figure 1 shows the handset, Figure 2 shows the handset, and Figure 2 shows the handset.
1. Yuchika, 0.3□6 waves. Ah,. (2) is a gate control circuit (pulse signal generation circuit) (4
) is a switch, spider is a counter, (In is a selection control circuit,
(to) is a balanced circuit.

Claims (1)

[Claims] (1) A side sound protection circuit for a wireless telephone device comprising a base unit connected to a telephone line and a slave unit connected to the base unit via wireless communication, wherein the base unit includes a switch and a slave unit connected to the base unit by wireless communication. A pulse signal generation circuit that generates a pulse signal in response to the operation of this switch is provided, and a counter and a side noise prevention circuit are provided that count the pulse signals transmitted from the child device to the parent device. 1. A side sound prevention circuit for a wireless telephone device, comprising: a plurality of balancing circuits; and a selection control circuit for selectively controlling the balancing circuit in response to an output of the counter.