JPH0378358A - Telephone set - Google Patents

Abstract

PURPOSE:To attain both the reduction of parts and the simplification of a control circuit by making a gain control circuit and a frequency characteristic control circuit common. CONSTITUTION:Gain controlling resistors R1 to R4, a low frequency characteristic controlling capacitor C1, a high frequency characteristic controlling capacitor C2, snd a gain-frequency characteristic controlling switch SW1 are provided. Now, when the switch SW1 is turned OFF, gain is determined by R1 and R2+R3, and frequency characteristic is determined by C2(R2+R3), and becomes a characteristic like a full line in a figure. When the switch SW1 is turned ON, output OUT is divided by resistors R3, R4, and feedback quantity is reduced, and the gain becomes larger as indicated by the dotted line. Besides, the frequency characteristic of a high frequency band is determined by R2 to R4 and C2, but by selecting R2 to R4 properly, cut-off frequency FH can be shifted to lower frequency. Thus, the reduction of the parts and the simplification of control can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of industrial application to which the invention pertains The present invention relates to a telephone with a gain adjustment function.

(2) Conventional technology and its problems Generally, when adjusting the receiving gain in a telephone, etc., if the gain is simply increased, acoustic coupling between sending and receiving calls occurs in a band slightly higher than the voice band, resulting in howling. This is the case. Therefore, it is generally difficult to adjust the reception gain so as to obtain a high reception volume in a stable state without causing howling.

(3) Purpose of the Invention The present invention makes it possible to obtain a high listening volume in a stable state by sharing the gain control and frequency characteristic control circuits, and also to reduce parts and simplify control. The aim is to provide a telephone that can

(4) Structure and operation of the invention FIG. 1 shows the main part of one embodiment of the invention. RI to R4 are resistors for gain adjustment, C0 is a capacitor for adjusting low frequency characteristics, C: is a capacitor for adjusting high frequency characteristics, and SWl is a switch for controlling gain frequency characteristics.

When switch SWI is turned off now, the gain is determined by R-r and R1+R3, and the frequency characteristic is Ct (Rz +R
s), and the characteristics are as shown by the solid line in FIG.

Next, when SWl is turned on, the output OUT is R:l, R4
The amount of feedback decreases, and the gain increases as shown by the dotted line. Also, the high frequency characteristics are R2-R4 and C
Although it is determined by t, the cutoff frequency F can be shifted to a lower frequency by appropriately selecting R2-R4.

Howling generally occurs at a frequency of about 2 KHz, so the frequency characteristic I shown by the solid line when a normal gain is provided and the frequency characteristic ■ shown by a dotted line when the gain is increased are the same as the above 2 KHz. Approximately 1.5dB in the vicinity
After suppressing the gain difference to a certain degree, it is possible to provide a gain difference of about 7.5 dB at IKHz, which includes the main fundamental wave component of voice. This makes it possible to perform high gain adjustment for the main fundamental wave component of the voice while ensuring howling margin.

FIG. 3 shows another specific example of the reception gain adjustment circuit.
In (a), the feedback resistors Rz and Rs are configured by a variable resistor VR, and in Φ), the variable resistor VR is connected to the human resistor R1, and a switch is connected between the input terminal of the amplifier and the intermediate terminal of the variable resistor VR. (C) is a switch S.
A variable resistor VR is inserted between the variable resistor VRO and the capacitor C3, and in (d), multiple resistors are installed in place of the variable resistor VRO in (C) and can be used by switching them sequentially or in any combination. It is composed of In either case, it is possible to obtain characteristics similar to those of the specific example shown in FIG.

The specific configuration and operation of the circuit shown in FIG. 4 will be explained.

■ Operation of the incoming circuit The incoming circuit is always connected to Ll-L2, and when an incoming signal is sent, it is full-wave rectified by the CD24, passes through the LED, and is applied to the vCC of the tone ringer IC. At the same time, TR9 is OPJed. to drive the buzzer S (sounder).

In addition, the DIP-5H allows you to switch the incoming call sensitivity and incoming sound quality to two levels each, and the incoming volume to three levels using the slide switch.

CD3 is a diode for reverse voltage protection of the LED, and CD20 is a varistor for overvoltage protection of the tone ringer IC. T
The purpose of R9 is to prevent the tone ringer IC from becoming a load when playing a beep or the like.

■ Electronic hook circuit a) When the handset is raised from the startup standby state with the hook needle, the hook needle (SW2
), the contacts A-B and CD are closed, and the line closing circuit LS is operated by making A-B. As a result, current is supplied to the speech network NW (IC) and a DC loop is formed. Also, when contact C-D is metered, the HS of the microcomputer CPU becomes "L" through TR13, and the microcomputer CPU detects that it is in off-hook mode and loops.
is set to "H" and current is supplied to the line closing circuit LS to maintain its operation.

In addition, in order to prevent the CPU from malfunctioning when the TR13 is started from the initial state, the input signal (HS) is input after VDD has completely risen, and if the line is disconnected while it is off or 7, the HS is set to "H". ``The function is to prevent current flow due to internal pull-up.

b) When the SP button is pressed in the start-up standby state by the SP button, the microcomputer C
The PU changes from sleeve mode to operation mode and starts key scanning. If the SP button is detected here, Loop will occur.
is set to "H", the line closing circuit LS operates, and a DC loop is formed.

■ Dial circuit a) DP sending circuit When the dial button is pressed in the DP mode, the DP repeats H-L for the corresponding number of times.

As a result, the line closing circuit LS repeats OFF and ON.

b) PB sending circuit When the dial is pressed in PB mode, the corresponding 2
The frequency is output from TONE-OUT of the microcomputer CPU. This is divided into resistors on the way, and one side is input to Bl of speech network N- and is heard from the handset and speaker as a PB confirmation tone, and the other side is input to MFI of speech network N-, and the other side is input to VL and line closing circuit LS.
It is sent to circuits LL and L2 via.

■ Hold circuit When the hold button HD is pressed during a call, the microcomputer CPU detects this and sets HD8 to "L". As a result, the melody
vo to IC. - Voltage between GND is ensured and Melody-I
A melody is output from the MO of C.

The transmission and confirmation sound below are the same as the PB transmission.

Also, at this time, even if you put down the handset, the microcomputer CPU
The line will not be disconnected because the Loop remains “H”.

■ Key Tone circuit and Beep circuit microcomputer c
When KT and Beep of pu are outputted at 2 KHz, TR18 repeats ON and OFF accordingly, and a 2 KHz signal is given to the 600Ω side of T3.

As a result, the voltage on the Ω side becomes about three times as high as that of the buzzer S.
(sounder).

■ Power supply circuit The power supply circuit E of the telephone consists of four elements: El... Power supply E2 using AAA batteries... Backup power supply E3 during standby... Power supply E4 during DP make... Low current circuit power supply During normal operation, the low current circuit of E4 maintains the current to about 3 cm, and AAA batteries are mainly used as a power source for memory backup.

■ R-UP circuit When the receiving volume switching button UP is pressed, the output terminal RUP of the microcomputer CPU becomes high (H) - mouth - (L), and the amount of negative feedback from the RC of the speech network NW changes the receiving gain adjustment circuit R-UP. Since the gain of the amplifier increases through the signal, the listening volume increases.

In addition, the volume of the call is set when dialing, ending a call, holding a call, etc.
It will be reset and the earphone volume will return to low.

■ Imaginary ground (IM-GND) circuit When the loop of the microcomputer CPU is closed and when the transfer signal is received, the group GND of the microcomputer CPU is momentarily set. /Placez, DP
/PB, 20/10.0AP10FF) to microcontroller C
It is read by the PU and performs functional operations according to the DIP-5 settings.

■ Branch bell circuit a) Sending circuit When buttons on dials 1 to 3 are pressed in hold mode,
An output signal corresponding to the dial button is output from SO of the microcomputer CPU. At the same time, the inverted signal of SCK, which outputs the synchronization signal, and the AND output of the AND circuit of the pending transfer section HT of the SO are input to the base of TR17, and the transmission pulse is sent from VL to the line closing circuit LS. It is sent to lines LL and L2 via.

b) When a transmitting pulse is sent from the VL of another branch partner telephone (not shown) in the reception circuit standby state, the pulse enters the primary side (110Ω) of the TI through C52.

Then, a voltage approximately 10 times higher appears on the secondary side (Ω at 11), and a signal is sent to the pending transfer unit HT.

Hold transfer unit l (inside T, in order to detect that the time difference between this rising signal and falling signal is the pulse width, the window is opened using the signal that was input first and the signal is input within a certain period of time (pulse width). Only the next signal is allowed to pass through.This eliminates noise.

The passed signal is waveform-shaped and compared with SCK (system lock) to recognize the data.

C) Transfer data The transfer data is sent in the pattern shown in Figure 5(a).
If the data match with a probability of 2/3 within 2/3, it is received at the timing shown in FIG.

[Phase] Keypad configuration As an example, the keypad has the following configuration.

1~0...Dial button HD...Hold button UP...Receiver volume switch button SP...Speaker button M...Register button F...Flash button */T...Aster and tone switch Button RD/P...
・Redial/pause buttons A, B, C...One-touch dial button (5) As described in detail of the invention, the present invention has a common gain adjustment circuit and frequency characteristic adjustment circuit, thereby reducing parts and improving control. This has the advantage that the circuit can be commonly simplified, and the gain of the main components of the voice can be increased while securing howling margin. Also, SWI can be a semiconductor switch.
By using the oven drain output of the CPU, simple control can be performed, and by using variable resistors for SW and R4, it is easy to make the gain and frequency characteristics continuously variable.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the main parts of an embodiment of the present invention, FIG. 2 is a frequency characteristic diagram of the embodiment of FIG. 1, and FIG. 3 is a circuit diagram showing another specific example of a receiving gain adjustment circuit used in the present invention. FIG. 4 is a specific circuit diagram of the telephone according to the present invention, and FIG. 5 is a time chart for explaining the operation of the specific example of FIG.

Claims (1)

[Claims] When increasing the receiving gain of a telephone, it is possible to adjust the gain with frequency characteristics such that the gain increase at the frequency that causes howling is sufficiently low compared to the gain increase for the main fundamental wave component of the voice. A telephone characterized by being configured with.