JPS61214849A - Telephone set - Google Patents

Abstract

PURPOSE:To prevent an uncomfortable impulsive tone from a speaker by not only cutting off a DC voltage to an amplifying circuit by a switching transistor TR but also muting the amplifying circuit by a muting TR when a dial signal is transmitted. CONSTITUTION:When dial buttons of a dial pulse generating circuit 13 are depressed for the purpose of transmitting the dial pulse signal, a muting signal is generated from the circuit 13, and a switching TR 23 is turned off to cut off the supply of the DC voltage to an amplifying circuit 22. Simultaneously, a muting TR 25 is turned on to mute the circuit 22. Therefore, the impulsive tone is not generated from a speaker 7 even if the DC voltage to the circuit 22 is changed quickly. When the transmission of the dial signal to the other party is terminated, a terminal MT goes to the high level again, and the signal applied to the TR 23 through an inverter 24 goes to the low level, and therefore, the TR 23 is turned on again to apply the DC voltage to the circuit 22, and the TR 25 is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a telephone set that can eliminate noise generated when transmitting dial pulse signals.

(b) Conventional technology Conventionally, when making a telephone call, a dial pulse signal for calling the other party was generated by turning a rotary dial and opening and closing a mechanical switch.
As described in Japanese Patent No. 0347, a dial pulse signal is electronically generated using an integrated circuit and transmitted to the other party via a telephone line. In order to actually transmit the dial pulse signal, the signal transmitted from the exchange via the telephone line is rectified in a rectifier circuit to obtain a DC voltage, and the DC voltage is intermittent with the dial pulse signal. This is done by intermittent telephone line signals and replacing them with dial signals.

(c) Problems to be Solved by the Invention By the way, in the above-mentioned telephone that electronically generates a dial pulse signal, by changing the function switch, it is possible for the other party to make a call by operating the dial button while the handset is placed on the hook stand. There are telephones that can perform operations such as lifting the handset to make a call. When generating a dial pulse signal in such a telephone, it is necessary to confirm that the telephone line is closed by operating a key button and listening to an oscillating sound from the telephone line before dialing in the key-in. Therefore, in the electronic telephone set, the oscillation signal is amplified by an amplifier circuit, the amplified oscillation signal is applied to a speaker, and the sound is emitted from the speaker, so that the oscillation sound (two-two tone) can be heard without lifting the handset. That's what I do.

The operating voltage for operating the amplifier circuit is the DC voltage used to transmit the dial pulse signal, so when transmitting the dial pulse signal, the DC voltage is continuously supplied to the amplifier circuit. If it remains as it is, the DC voltage will drop and the dial pulse signal cannot be transmitted. Therefore, in order to generate a dial pulse signal, when the dial key is pressed in, the transistor is turned off to cut off the DC voltage to the amplifier circuit. Therefore, when the DC voltage is cut off, the operating voltage of the amplifier circuit changes rapidly, which becomes a noise signal that is applied to the speaker, causing the speaker to generate an impact sound. The present invention aims to eliminate the above-mentioned drawbacks by performing a muting operation on the amplifier circuit when cutting off the DC voltage to the amplifier circuit in order to prevent such impact noise from occurring.

(b) Means for Solving the Problems The telephone of the present invention has a rectifier circuit that rectifies signals applied from a telephone line to obtain a DC voltage, and a dial pulse signal that generates a number of dial pulse signals according to the number of buttons operated. a generating circuit, a dial signal generating means for generating a dial signal to be transmitted to the other party by intermittent the DC voltage in response to the dial pulse signal, and an opening/closing circuit that is turned on and off by the muting signal generated by the dial pulse signal generating circuit. a transistor, an amplifier circuit that is activated by the DC voltage applied via the switching transistor and that amplifies the audio signal supplied via the telephone line and drives a speaker, and a dial generated by the dial signal generation circuit. Turns on or off with a pulse signal.

and a muting transistor for muting the amplifier circuit.

(E) Function Since the telephone of the present invention has the above-described configuration, when the dial button of the dial pulse signal generation circuit is pressed in order to transmit a dial pulse signal, a muting signal is generated from the dial pulse signal generation circuit. Turn off the switching transistor and cut off the supply of DC voltage to the amplifier circuit. At the same time, turn on one muting transistor.

Since the amplifier circuit is muted, even if the DC voltage to the amplifier circuit suddenly changes, no impact noise will be generated from the speaker. Further, the dial signal generating means is operated by the dial pulse signal, and the DC voltage is turned on and off to send a dial signal to the telephone line.

(v) Embodiment An embodiment of the telephone according to the present invention will be described with reference to the drawings.
1) is a first rectifier circuit connected to the telephone line (Ll) via first and second changeover switches (2) and (3); (4) is connected to the first rectifier circuit (1); The output of the ringer signal detection circuit is
5) and the speaker (7) via the third switch (6).
). (8) is a telephone line (L, ) (Lz)
<A second rectifier circuit connected via the first and second changeover switches, (9) is a display circuit, and the positive electrode at one end is connected to the first rectifier circuit (1) and the second rectifier circuit (8). The collector is connected to the negative electrode of the light emitting diode member, and the emitter is connected to the first rectifier circuit (1
) while the ringer is connected to the base.
A first display transistor circle is turned on and off by a detection signal from a detection circuit (4), a collector is connected to the negative electrode of a light emitting diode a1 together with a collector of the first display transistor aυ, and an emitter is connected to a second rectifier circuit (8). ) and a second display transistor Cl5O connected to [
0 is a dial pulse signal generation circuit that generates a number of dial pulse signals corresponding to the pressed key button when a key button of the keyboard I is pressed, and generates a pulse signal generated by operating the key button. DP terminal that outputs a muting signal that changes from high level to low level when the key button is pressed.
It has a T terminal, and the DP terminal and MT terminal are connected to a diode (
15α to the base of the second display transistor α2. αη is a dial transistor connected to the second rectifier circuit (8), which intermittents the DC voltage of the second rectifier circuit (8) every time a dial pulse signal generated from the dial signal generating circuit α is applied. generates a dialing signal and connects the telephone line (Ll) (Ll)
transmitted to the other party via. (Left) A speech circuit connected to the second rectifier circuit (1) via a fourth changeover switch (19), to which a handset (A) is connected. (2
1) is the speech circuit (11 and the fourth changeover switch α9).
A line transformer is selectively connected to the second rectifier circuit (8) at the line transformer, and its output is applied to the amplifier circuit (8). (
C) is the second rectifier circuit (8) and the fourth changeover switch α1.
A switching transistor connected between the dial pulse signal generating circuit 03 is turned on and off by the muting signal generated from the dial pulse signal generation circuit 03, and when transmitting the dial signal to the telephone line (Ll) (L,), the second rectifier circuit (8) This prevents the rectified DC voltage from being supplied to the amplifier circuit (A).

(C) is a muting transistor that is turned on and off by the dial pulse signal of the dial pulse generating circuit 0.

Note that the first and second changeover switches (21(3)) are located in the state shown in the figure when in a standby state waiting for a call from the other party. When the function button 13+ is switched to the hook-off state, it is switched to a state different from that shown in the figure, and the third changeover switch (6) is in the state shown when the function button 7 is turned on, and the fourth changeover switch (6) is in the state shown in the figure when the function button 7 is turned on. When the handset (A) is on the hook stand, it is in the state shown in the figure, and when the handset handle is lifted from the hook stand, it is switched to the opposite side as shown in the figure.

Also, the audio circuit that transmits the audio signal to the speech circuit α barrel or the line transformer (21) is omitted because it is not the gist of the present invention.

The operation of the telephone according to the present invention will be explained. When making a call to the other party, a function button (not shown) is pressed and the first and second changeover switches (2H3) are switched to a state different from that shown. Then, the telephone line (Ll) (Lt
) is rectified by a second rectifier circuit (8) to produce a DC voltage. The DC voltage is supplied to the dial pulse signal generation circuit αJ, which operates the dial pulse signal generation circuit 0 to generate a direct current signal from the terminal (MT). The direct current signal is inverted by an inverter and applied to the switching transistor (c), turning on the switching transistor (c). Therefore, the second rectifier circuit (8)
The rectified DC voltage is applied to the °C amplifier circuit via the line transformer I21) to put the amplifier circuit 122 into operation. On the other hand, the oscillation signal (two,
The second signal) is connected to the line transformer 121 via the audio circuit (not shown) from the first and second changeover switches (2) and (3).
, is further supplied to the amplifier circuit, and after being amplified by the amplifier circuit @, is applied to the °C speaker (power) via the third changeover switch (6), which is in a state different from that shown in the figure.Therefore, from the speaker (7), the two, A beep will be generated, confirming that the telephone line has been closed.If you press the key button for the other party's telephone number in such a state, the number of dial pulse signals corresponding to the pressed key button will be emitted. Since the dial transistor αη is turned on and off each time a dial pulse signal is applied, the DC voltage of the second rectifier circuit (8) is intermittent, and the signals of the telephone lines (Ll) (Lt) are also intermittent and transmitted as a dial signal to the other party. At this time, if DC voltage is continued to be supplied to the amplifier circuit, the second rectifier circuit (
8), the DC voltage may drop and a sufficiently large dial signal may not be obtained. However, when the key button is pressed, the muting voltage of the terminal MT, which was at high level until then, becomes low level, and the switching transistor (c) is turned off, cutting off the DC voltage to the amplifier circuit □□□. However, since the power supply voltage of the amplifier circuit (2) suddenly changes to zero, the DC component of the output of the amplifier circuit (22) also changes rapidly, becoming a pulse signal that is applied to the speaker (7). An impact sound will be generated from the speaker (7). However, in the present invention, when the switching transistor (C) is turned off, the muting transistor (C) is turned on by the dial pulse signal, and the amplifier circuit @ is turned on. Since muting is used, the impact sound is not generated from the speaker (7).

Further, the dial pulse signal is transmitted through the diode ae.

and turns on the second display transistor a'IJ every time a dial pulse (1) is added. On the other hand, one end of the light emitting diode α0 is connected to the DC voltage of the second rectifier circuit (8). is added, each time the second display transistor α2 is turned on, the light emitting diode α@ emits light, indicating that the dial pulse signal is being transmitted to the other party. When the process is finished, the terminal MT becomes high level again, and the signal applied to the switching transistor (c) via the inverter c24) becomes low level, so the switching transistor (c) turns on again and applies a DC voltage to the amplifier circuit. Also, turn off the muting transistor (c). Therefore, the calling signal calling the other party, or the voice signal that the other party speaks upon hearing the calling signal, is applied to the amplifier circuit (2+(3)) via the first and second changeover switches (2+(3)) as described above. After being amplified by the speaker (7)
Since the telephone is supplied to the telephone and drives the speaker (7), the owner of the telephone can perform operations from key-in to when the other party picks up the handset and makes a call without using the handset. When the other party makes a call, the owner turns on the handset■
When the user lifts the phone from the hook stand and hooks it off, the fourth changeover switch α1 is switched to the opposite side as shown in the figure, so the handset (A) is connected to the speech circuit (18). You can listen to messages and transmit your own messages to the other party.

Also, when a ringer signal arrives via the telephone line (Ll) (Lt) in a standby state waiting for an incoming call from the other party, the ringer signal is detected by the ringer signal detection circuit (4). The speaker (7) emits a sound, and all the light emitting diodes emit light to indicate the fact. (G) Effects of the Invention As described above, the telephone of the present invention rectifies the signal from the telephone line using the rectifier circuit. to obtain a DC voltage, and supply the DC voltage to the °C amplifier circuit via a switching transistor that is turned on and off by a signal obtained from a dial pulse signal generation circuit, in which a muting transistor is turned on and off together with the switching transistor, Therefore, even if the power supply voltage supplied to the DC amplifier circuit changes by turning off the switching transistor when transmitting a dial signal and the DC component of the output changes rapidly, the change will be suppressed by the muting transistor by ℃. It is possible to prevent unpleasant impact noises generated from speakers.

[Brief explanation of drawings]

The figure is a circuit diagram of a telephone according to the invention. (8)...Second rectifier circuit, αJ...Dial pulse signal generation circuit, α4)...Keyboard, (I7
)...dial transistor, (21)...line transformer, (2z...amplifier circuit, threat...opening/closing transistor, (c)...muting transistor.

Claims (1)

[Claims] (1) A rectifier circuit that rectifies a signal applied from a telephone line to obtain a DC voltage, a dial pulse signal generation circuit that generates a number of dial pulse signals according to the number of operated buttons, and a DC voltage generated by the dial pulse signal. dial signal generating means that generates a dial signal to be transmitted to the other party by intermittent voltage; a switching transistor that is turned on and off by a mute signal generated by the dial pulse signal generating circuit;
an amplifier circuit that is activated by the DC voltage applied via the switching transistor and that amplifies the audio signal supplied via the telephone line and drives a speaker; and a dial pulse signal generated by the dial signal generator circuit. and a muting transistor that mutes the amplifier circuit by turning on or off, and when transmitting a dial signal, the switching transistor cuts off the DC voltage to the amplifier circuit,
A telephone characterized by muting an amplifier circuit using a muting transistor.