JPH0413864Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a telephone circuit equipped with a dial circuit that uses a loop current as a power source.

[Conventional technology]

Telephones using semiconductor devices are equipped with an integrated circuit dial circuit, and part of the loop current that passes through the DC loop that is closed in response to off-hook is used as the power source for the dial circuit, and is used to send out dial pulses. Shunting the loop current from a part via the pulse sending circuit inserted into the DC loop and giving it to the dial circuit,
A power supply holding capacitor is connected between the power supply terminals of the dial circuit, and a diode is inserted into the power supply path to prevent the capacitor from discharging.

[Problem that the invention attempts to solve]

However, in order to retain the dial number stored in the redial memory in the dial circuit for a long time, it is necessary to increase the capacitance of the capacitor. Due to the relationship with the resistance value in the loop circuit, the rise in the terminal voltage of the capacitor is delayed, and the time required from off-hook to when the dial circuit becomes operational becomes longer, making it difficult to dial immediately after off-hook. This creates a problem where it is not possible to do so.

[Means for solving problems]

In order to solve the above-mentioned problem, the present invention is constructed by the following means.

That is, in the above telephone, a first capacitor C2 with a relatively small time constant that maintains the power supply and quickly increases the terminal voltage is connected in parallel with the power terminal of the dial circuit, and this first capacitor C2 is connected in parallel with the power terminal of the dial circuit. On the other hand, second capacitors C3 and C4, which are connected in parallel through a resistor R4 and have a larger time constant than the first capacitor and which similarly maintain the power supply, are provided.

[Effect]

Therefore, in response to off-hook, the first capacitor is quickly charged and the dial circuit is immediately ready for operation, while the second capacitor is gradually charged through the resistor, and the first capacitor is not charged. In addition, since the power supply is continued by discharging through the resistor even after on-hook, the dial number can be retained by the redial memory in the dial circuit for a long time.

〔Example〕

Hereinafter, details of the present invention will be explained with reference to figures showing embodiments.

The figure is a block diagram, in which line terminals L ₁ and L ₂ to which telephone lines from the exchange are connected are connected to a switch HS ¹ and a diode bridge (hereinafter referred to as
A telephone circuit (hereinafter referred to as TKC) 2 is connected via DB) 1, and a switch HS ¹ that responds to off-hook
When DB1 is turned on, the DC loop via TKC2 is closed, and the loop current, which has a constant polarity due to DB1, is passed to TKC2, and accordingly, the receiver R and the transmitter in the handset connected to TKC2 are connected to TKC2. You can freely make calls using device T.

However, between DB1 and TKC2 of the DC loop, the collector-emitter of a transistor (hereinafter referred to as TR) Q ₁ that constitutes a pulse sending circuit is inserted, as well as TR Q ₂ and a resistor R ₁ to _R3 are provided, and the base of TR/ _Q2 is connected to the pulse output of a dial circuit (hereinafter referred to as DIC) 3.

Note that the TKC2 uses an integrated circuit that includes a receiving amplifier and a transmitting amplifier.
Power is supplied to DIC3 and the peripheral circuits from the power decoupling terminal connected to the bypass capacitor _C1 , and the gate and source are connected to the power supply path leading to the positive power supply terminal VD of DIC3. A V (vertical groove) MOS type TR with a diode connected between the drain and the source.
Q ₃ is inserted and the power terminal VD/VS
A first capacitor C ₂ for power retention is connected between them, and second capacitors C ₃ and C ₄ are connected in parallel to capacitor C ₂ via a resistor R ₄ for the same purpose. , TR・Q ₃ is inserted in the direction to prevent these discharges.

Furthermore, a pull-up resistor _R5 is connected between the positive power supply terminal VD and the hook switch signal terminal of the DIC3, and a hook switch ^HS2 is connected between the same terminal HS and the negative power supply terminal VS.
is connected between the collector and emitter _of TR・Q ₄ used as a switching element.
A forward bias is applied to the base of TKC2 from the power decoupling terminal of TKC2 through resistors _R6 and _R7 .

Note that the capacitor _C5 is connected as a bypass for noise components.

Therefore, the off-hook causes the off-hook to switch.
When HS ¹ turns on, the rectified output of DB1 immediately occurs and is applied as a forward bias to the base of TR Q ₂ through resistor R ₃ , and accordingly TR Q ₂ turns on, Through resistor R ₂
Connect the base of TR・Q ₁ to the negative output of DB1,
In order to provide forward bias, TR·Q ₁ is also turned on, and the DC loop via TKC 2 is immediately closed.

Note that the pulse output of the DIC 3 has a high impedance when no power is applied, and does not interfere with the supply of forward bias through the resistor _R3 .

When TR・Q ₁ turns on, the loop current via TR・Q ₁ flows to TKC2, and a part of this causes
Capacitor C ₂ is first charged rapidly via TR Q ₃ , and as the terminal voltage rises, power is supplied to DIC 3, TR Q ₄ is turned on, and switch HS ² is also turned on. As a result, the switch signal terminal changes from "H" (high level) to "L" (low level), thereby canceling the operation inhibition state of DIC3 and changing the pulse signal to "H".
enters the standby state and presses the dial key (hereinafter referred to as
If DK) 4 is operated, the pulse output will repeatedly send out "L" and "H" accordingly, and TR・Q ₂ and Q ₁ will turn off and on accordingly. , TR・Q ₁ is turned off and on to send out a dial pulse, and if the other party responds by connecting the exchange in response to the exchange, the call can be made freely as described above.

In addition, even if TR Q ₁ is turned off during dial pulse transmission, the _DIC
At the same time, capacitors C ₃ and C ₄ with larger capacities are charged via resistor R ₄ , and even after on-hook, power is supplied to DIC 3 via resistor R ₄ . To do this, DIC3
Dial numbers stored in the internal redial memory can be retained for a long time.

In addition, due to the connection described above, the VMOS type TR Q ₃ has a low forward saturation voltage of approximately 0.4V as a diode even at low currents, reducing the voltage drop by approximately 0.1 to 0.2V compared to a normal diode. Accordingly, even if the line voltage of the telephone line decreases, DIC3
operation can be ensured.

Note that it will be more effective if a VMOS type TR connected as a diode is used for the diode of DB1 as well as TR/ _Q3 .

In addition, the DIC3 power supply holding capacitor is C ₂
Since the capacitor C2 is divided into _C4 and the resistor _R4 is inserted into the larger capacitance, the terminal voltage rises quickly due to capacitor _C2 charging, and DIC3 immediately responds to DK4 operation in response to off-hook. As the voltage increases, capacitors C ₃ and C ₄ are gradually charged via resistor R ₄ without affecting the charging of capacitor C ₂ .

That is, for example, the values of capacitors C ₂ , C ₃ , and C ₄ are set to 220 μF, 1000 μF, and 1000 μF, and the value of resistor R ₄ is set to several tens of kΩ, and a DC voltage is applied depending on the off-hook. Since the capacitor _C2 , which has a relatively small capacity, has a small time constant, the terminal voltage rises to the applied voltage in a short time, and this voltage is supplied to the DIC 3, which immediately becomes ready for operation. And during this time, a large capacitor
Since C ₃ and C ₄ have a large time constant, they are slowly charged through resistor R ₄ and the terminal voltage rises to the applied voltage.

On the other hand, even if the DC voltage is no longer applied due to on-hook, the input impedance of DIC3 is large, so the charges accumulated in capacitors _C3 and _C4 are slowly discharged through resistor _R4 , and the power supply to DIC3 is interrupted. conduct. Therefore, the DIC 3 can hold the dial number stored in the redial memory for a long time.

On the other hand, a hold switch MS ¹ is connected in parallel to the lock switch HS 1 via DB 5 and a diode D for blocking loopback, and a hold switch MS ¹ is connected in parallel to the lock switch HS 1.
A hold switch ^MS2 is connected between the negative output of TKC2 and TKC2.
is inserted, and the same switch is activated depending on the operation.
When MS ¹ and MS ² perform self-hold, the same switch
MS ¹ bypasses the switch HS ¹ , and
The DC loop is opened by the hold switch ^MS2 , and the anode and cathode of the thyristor SCR are connected to this part via DB5.

In addition, a constant current circuit (hereinafter referred to as CIC) 6 is connected to the diode D side of the hold switch MS ¹ via a hold switch HS ³ , and thereby a resistor R ₈
A trigger current is applied to the gate of a thyristor SCR connected to a capacitor _C6 for bypassing noise components.

Therefore, the hold switch during off-hook
When MS ¹ and MS ² are operated, the thyristor is activated via the switch HS ³ and CIC 6, which are turned on.
A trigger current is applied to the gate of SCR, which turns on and closes the DC loop via TKC2 and holding switch ^MS2 , so the loop current maintains the on state of thyristor SCR even when on-hook is performed. Set pending status.

However, while the handset was left on hold off-hook and left on a tabletop, etc., it was accidentally
When DK4 is operated, DIC3 responds, and the DC loop is interrupted by turning TR/ _Q1 off and on. Due to the intermittent holding current of the thyristor SCR, maintaining the on state becomes unstable, and there is a risk of releasing the hold state. Due to the operation of the hold switch,
The operation of DIC3 is prohibited.

That is, an inverter is provided with resistors R ₉ to R ₁₁ and TR Q ₅ , and when the hold switch MS ¹ is turned on, these power supplies are applied, and TR Q _{5 is}
turns on, sets the collector potential to which the power supply is applied through resistor _R11 to "L", and turns off TR _Q4 , so even if the switch ^HS2 is on, the switch signal terminal is forced to becomes “H” and the DIC3 becomes in a state where operation is prohibited.

Note that with the hold circuit using the thyristor SCR, if the hold switch is operated during off-hook, the hold state will be entered via the thyristor SCR, but even if the hold switch is accidentally activated during on-hook, the hold switch HS ³ will not turn off. , no trigger current is given to the gate of the thyristor SCR,
Thyristor SCR remains off and does not close the DC loop.

Additionally, if a call is placed on hold and the other party goes on-hook during this time, the exchange sends a busy tone and a howler tone, and then temporarily releases the line, so the loop current is disconnected at this time. In response to this, the thyristor SCR does not lose the holding current and returns to OFF, automatically canceling the holding state and opening the DC loop.

This completely prevents the setting of a hold state due to an erroneous operation during an on-hook, and the continuation of an unnecessary hold state when the other party goes on-hook after setting a hold state during a call, and prevents calls from being unable to be received due to telephone line capture. definitely excluded.

It should be noted that the hold switch is generally one that can be restored by re-operation and also works in conjunction with a hook switch and can be restored by off-hook.

However, depending on the conditions, use a general diode instead of TR・Q ₃ and connect it from between TR・Q ₁ and TKC2.
Power can be supplied to DIC 3, resistors can be inserted into capacitors C ₃ and C ₄ individually, and the same can be applied to cases where audio composite frequency is used as a dial signal. Various modifications are possible. is free.

[Effect of idea]

As is clear from the above explanation, according to the present invention, the dialing circuit can immediately operate in response to off-hook, and the redial memory can retain the dialed number for a long time, so it is very useful in various telephones. Effects can be obtained.

[Brief explanation of drawings]

The figure is a circuit diagram showing an embodiment of the present invention. 2...TKC (Telephone circuit), 3...DIC (Dial circuit), 4...DK (Dial key), L ₁ , L ₂ ...
Line terminal, Q ₁ ~ Q ₅ ...TR (transistor), C ₁ ~
C ₆ ... Capacitor, VD, VS ... Power supply terminal, R ₁
~ _R11 ...Resistor.

Claims (1)

[Scope of Claim for Utility Model Registration] In a telephone equipped with a dial circuit whose power source is a loop current passing through a DC loop that is closed in response to off-hook, and which has a capacitor for maintaining the power supply, a first capacitor connected in parallel that quickly raises the terminal voltage and maintains the power supply with a relatively small time constant; and a first capacitor connected in parallel to the first capacitor via a resistor. 1. A telephone circuit comprising: a second capacitor for holding the power supply and having a larger time constant than the first capacitor.