JPH036056Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention provides a display circuit for a telephone set in which a display element that displays the transmission status of a dial signal is dimmed at a constant brightness. .

(b) Prior Art First, as described in Japanese Patent Application Laid-Open No. 59-30347, an electronic telephone set used an integrated circuit to electronically generate a dial pulse signal and transmit it to the other party via a telephone circuit. is often used.
It is known that such electronic telephones light up a lamp to indicate that they are in use, as described in Japanese Patent Laid-Open No. 59-75750. However, with electronic telephones, dial pulse signals are sent to the other party by simply pressing a key button on the keyboard, so the owner of the telephone has to display some kind of display to confirm that the dial pulse signal is being transmitted. Although it is necessary to do so, none of the above-mentioned publications describes the use of such a display.

(c) Problems to be solved by the invention In order to solve this inconvenience, when transmitting a dial signal to the other party, a switching transistor is activated by a dial pulse signal generated by a dial pulse signal generation circuit by the operation of a key button. It turns on and off, and generates a dial signal by intermittent DC voltage that is supplied from the telephone line and whose polarity can be determined by the rectifier circuit.
The dial signal is transmitted to the other party via a telephone line, and the applicant has previously filed a patent application for displaying the transmission status of the dial signal by using the dial signal to turn off a light emitting diode. However, since the DC voltage obtained by determining the polarity in the rectifier circuit fluctuates during transmission of the dial signal, the dimming brightness of the light emitting diode is not constant. That is, when generating a dial signal in an electronic telephone,
Before dialing in, it is necessary to confirm that the telephone line has been closed by operating the key buttons and listening to the oscillating sound from the telephone line. Therefore, in the electronic telephone, the oscillation signal is amplified by the amplifier circuit of the audio side circuit, the amplified oscillation signal is applied to the speaker, and the sound is emitted from the speaker, so that the oscillation sound ( I made it so that I could hear the "two-two sound". Since the operating voltage for operating the amplifier circuit is the DC voltage used to transmit the dial pulse signal, the DC voltage is continuously supplied to the amplifier circuit when transmitting the dial pulse signal. If it remains as it is, the DC voltage will drop and the dial pulse signal cannot be transmitted. Therefore, when the dial key is pressed to generate a dial pulse signal, the transistor is turned off and the DC voltage to the amplifier circuit is cut off, so the DC voltage obtained by determining the polarity in the rectifier circuit also fluctuates, and the dimming brightness of the light emitting diode also fluctuates. do. The present invention provides a display circuit for a telephone that eliminates such drawbacks.

(d) Means for Solving the Problems The display circuit of the telephone of the present invention includes a rectifier circuit that determines the polarity of the voltage supplied from the telephone line, and a dial pulse signal generated by a dial pulse signal generating circuit that turns on and off according to the polarity. a first switching element that converts the determined voltage into a dial signal;
a display transistor controlled by a signal generated by the dial pulse signal generation circuit; a display element to which the dial signal is applied via the display transistor; a constant voltage element connected in parallel to the display element; and a second switching element that blocks the voltage on the output side of the rectifier circuit whose polarity has been determined when a dial signal is generated from being supplied to the audio side circuit.

(E) Function The display circuit of the telephone of the present invention has the above-described configuration, so that when transmitting a dial signal, the display transistor is controlled by the signal generated by the dial pulse signal generation circuit, and the display is displayed via the display transistor. The dial signal is applied to the element, and the display element is decremented to indicate that the dial signal is being transmitted. At this time, since the constant voltage element is connected in parallel to the display element, fluctuations in the voltage applied to the display element on the output side of the rectifier circuit are prevented.

(F) Embodiment An embodiment of the telephone according to the present invention will be described with reference to the drawings. Reference numeral 1 denotes a first rectifier circuit connected to telephone lines L ₁ and L ₂ via first and second changeover switches 2 and 3. ,
4 is a ringer signal detection circuit connected to the first rectifier circuit 1, the output of which is sent to a speaker 7 via a matching transformer 5 and a third changeover switch 6.
added to. 8 determines the polarity of the signals supplied from the telephone lines L ₁ and L ₂ .
a second rectifier circuit connected to the changeover switches 2 and 3;
Reference numeral 9 denotes a display circuit, which is connected in parallel to a light emitting diode 10a whose positive electrode at one end is connected to the first rectifier circuit 1 and the second rectifier circuit 8 in order to prevent fluctuations in the voltage applied to the light emitting diode 10a. The connected Zener diode 10b has a collector connected to the negative electrode of the light emitting diode 10a, and an emitter connected to the first rectifier circuit 1, while a detection signal from the ringer detection circuit 4 is supplied to the base. A first display transistor 11 that is turned on and off, and a collector whose collector is the first display transistor 1
The second display transistor 12 has a collector connected to the negative electrode of the light emitting diode 10a and an emitter connected to the second rectifier circuit 8. Reference numeral 13 denotes a dial pulse signal generation circuit that generates a number of dial pulse signals corresponding to the number of pressed key buttons when a key button of the keyboard 14 is pressed, and generates a pulse signal generated by operating the key button. outputs a muting signal that changes from high level to low level when the key button is pressed.
The DP terminal and the MT terminal are connected to the second display transistor 1 via diodes 15 and 16.
Connected to the base of 2. Reference numeral 17 denotes a dial transistor connected to the output side of the second rectifier circuit, which is turned on every time the dial pulse signal generated from the dial pulse signal generation circuit 13 is applied, and is connected to the output side of the second rectifier circuit 8. Generates a dial signal by intermittent voltage. Reference numeral 18 denotes a speech circuit having a handset 20, which together with an amplifier circuit 22 coupled to a line transformer 21 constitutes an audio side circuit, and is switched by a fourth changeover switch 19. Reference numeral 23 denotes an open/close transistor connected between the second rectifier circuit 8 and the audio side circuit, which is turned on and off by the muting signal generated from the dial pulse signal generation circuit 13, and when the dial signal is transmitted, the polarity is determined by the second rectifier circuit 8. The DC voltage generated is prevented from being supplied to the audio side circuit.
Reference numeral 25 denotes a muting transistor that is turned on and off by the dial pulse signal from the dial pulse generating circuit 13.

The first and second changeover switches 2 and 3 are placed in the state shown in the figure in a standby state in which they are waiting for a call from the other party. When the function button is switched to the hook-off state, the third switch 6 is switched to the state shown in the figure when the function button is switched to the hook-on state, and the fourth switch 19 is switched to the state shown when the handset 20 is on the hook. When the handset 20 is in the position shown in FIG.

Also, the speech circuit 18 or line transformer 2
The audio side circuit of the portion that transmits the audio signal to 1 is omitted because it is not the gist of the present invention.

Next, the operation of the display circuit 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 to switch the first and second changeover switches 2 and 3 to a state different from that shown. Then, the signals supplied from the exchange via the telephone lines L ₁ and L ₂ produce a DC voltage whose polarity is determined by the second rectifier circuit 8 . The DC voltage is supplied to the dial pulse signal generation circuit 13, which operates the dial pulse signal generation circuit 13 to generate a direct current signal from the terminal (MT). The direct current signal is sent to the inverter 24
The signal is inverted and applied to the switching transistor 23, turning on the switching transistor 23. Therefore, the DC voltage whose polarity is determined by the second rectifier circuit 8 is applied to the amplifier circuit 22 via the line transformer 21, thereby putting the amplifier circuit 22 into an operating state. On the other hand, the oscillation signal (two, two signal) transmitted from the exchange is transmitted from the first and second changeover switches 2 and 3 to the line transformer 21 via the audio side circuit (not shown).
Furthermore, it is supplied to the amplifier circuit 22, and the amplifier circuit 22
After being amplified, the signal is applied to the speaker 7 via the third changeover switch 6, which is in a different state from that shown in the figure. Therefore, since the speaker 7 generates a two-two tone, it is confirmed that the telephone line has been connected. When the key button for the other party's telephone number is pressed in such a state, a number of dial pulse signals corresponding to the pressed key button are generated as shown in FIG. Therefore, the DC voltage of the second rectifier circuit 8 is interrupted as shown in _{FIG .}
sent to the other party via. The dial pulse signal generated from the DP terminal of the dial pulse signal generation circuit 13 is also applied to the base of the second display transistor 12, and in order to turn on the second display transistor 12, the light emitting diode 10a and the second display transistor 12 are turned on. The dial signal flows through the dial signal. Therefore, the light emitting diode 10a blinks to indicate that a dial signal is being transmitted. By the way, if DC voltage is continued to be supplied to the audio side circuits such as the amplifier circuit 22 while the dial signal is being transmitted, the DC voltage of the second rectifier circuit 8 will drop, making it impossible to obtain a sufficiently large dial signal. Then, by pressing the key button, the muting voltage of the terminal MT of the dial pulse signal generation circuit 13 is set to the second level.
As shown in FIG. C, the signal is changed from a high level to a low level and is added to the base of the switching transistor 23, turning off the switching transistor 23 and cutting off the amplifier circuit 22. When the key operation is completed, the muting voltage becomes high level again, but at the same time, the dial pulse signal becomes low level and turns off the dial transistor 17, so the key operation is terminated due to the DC characteristics of the audio side circuit. When this happens, the DC voltage of the second rectifier circuit 8 fluctuates (FIG. 2A). At this time, since the muting voltage is applied to the second display transistor 12 and it is turned on, the variation in the DC voltage is applied to the light emitting diode 10a. Therefore, the brightness of the light emitting diode 10b may change, but in the present invention, since the Zener diode 10b is connected to the light emitting diode 10b, the fluctuation is suppressed and the brightness of the light emitting diode 10b does not change.

After the transmission of the dial pulse signal is completed, a calling signal for calling the other party is applied from the line transformer 21 to the amplifier circuit 22 via the telephone lines L ₁ and L ₂ through a voice side circuit (not shown). At this time, since the DC voltage rectified by the second rectifier circuit 8 is supplied to the amplifier circuit 22 via the switching transistor 23, the amplifier circuit 22 is in an operating state and the calling signal is amplified and applied to the speaker 7. Therefore, since the sound is emitted from the speaker 7, the owner can hear the ringing tone without having to lift the handset 20. When it is confirmed that the other party heard the ringing tone and lifted the handset to close the telephone lines _L1 and _L2 ,
When the handset 20 is lifted, the fourth changeover switch 19
is switched in the opposite direction as shown, activating the speech circuit 18. Therefore, since the handset 20 is now connected to the telephone lines L ₁ and L ₂ , the owner's message is transmitted from the handset 20 through the speech circuit 18 , the audio circuit, and the first and second changeover switches 2 and 3 . It is added to telephone lines L ₁ and L ₂ and transmitted to the other party. Also, a message from the other party enters the handset 20 via the reverse route to that described above and can be heard on the handset 20.

The light emitting diode 10a also displays an incoming call signal from the other party in the standby state. That is, when the handset 20 is placed on a hook stand (not shown) and is turned on without operating a function button (not shown) and is in a standby state as shown in the figure, when a ringer signal is transmitted from the other party, The ringer signal is applied to the first rectifier circuit 1 via the first and second changeover switches 2 and 3, where it is rectified, and further supplied to the ringer signal detection circuit 4, where it is converted into a ringing signal of a predetermined period. The calling signal is sent to the speaker 7 through the matching transformer 5 and the third changeover switch 6.
is applied, and a ringing tone is emitted from the speaker 7. At the same time, the detection signal converted into a pulse signal of a predetermined period by the ringer signal detection circuit 4 is applied to the base of the first display transistor 11, turning the first display transistor 11 on and off intermittently. On the other hand, since a smoothed current obtained by smoothing the ringer signal by the capacitor 27 flows through the positive electrode of the light emitting diode 10a, the light emitting diode 10a is switched on every time the first display transistor 11 is turned on.
A smoothing current flows through the light emitting diode 10a to indicate that the ringer signal has been received, so that even a telephone without a speaker 7 can know that the ringer signal is being received.

(G) Effects of the invention As mentioned above, the display circuit of the telephone according to the invention is as follows.
Since a constant voltage element is connected in parallel to the display element, the DC voltage on the output side of the rectifier circuit used to generate the dial signal is switched and supplied to the audio side circuit, and the output of the rectifier circuit applied to the display element is Even if the DC voltage on the side changes, the lighting brightness of the display element can be prevented from changing.

[Brief explanation of the drawing]

FIG. 1 is a display circuit diagram of a telephone according to the present invention, and FIGS. 2A to 2C are signal waveform diagrams of various parts of the present invention. 8...Second rectifier circuit, 9...Display circuit, 10a
...Light emitting diode, 10b...Zena diode, 12...Second display transistor, 13...
Dial pulse signal generation circuit, 17... open/close transistor, 18... speech circuit, 22... amplifier circuit.

Claims (1)

[Scope of utility model registration request] a rectifier circuit that determines the polarity of the voltage supplied from the telephone line; a first switching element that is opened and closed by a dial pulse signal generated from a dial pulse signal generating circuit and converts the polarity-determined voltage into a dial signal; and the dial. a display transistor controlled by a signal generated by a pulse signal generation circuit, a display element to which the voltage of the rectifier circuit is applied via the display transistor, and a constant voltage element connected in parallel to the display element; A display circuit for a telephone set, comprising a second switching element that blocks the voltage on the output side of the rectifier circuit whose polarity has been determined when the dial signal is generated from being supplied to the audio side circuit.