JPS632452A - Telephone set circuit - Google Patents

Abstract

PURPOSE:To surely make a talk through a speaker phone even if an exchange whose line voltage rises slowly is used so as to prevent any defective talk even when a wrong operation takes place during the talk, by making the electric current from a line to flow to the base of a transistor without any capacitor. CONSTITUTION:When a switch 13 is turned on without lifting up a handset, the electric current from a line is made to flow to the base of a transistor TR 15 and another TR 9 is turned off because a power supply switch 6 is opened. Even if the rise of the line voltage of an exchange is slow, the TR 15 is turned on and the electric current flows to a relay coil 14. As a result, a change-over switch 4 and the power supply switch 6 are closed and an off- hook state is set. When the switch 6 is closed, the TR 9 is turned on and diodes 11, 12, and 22 are earthed. Therefore, the current supply to the base of the transistor 15 is cut off and the TR 15 is turned off. Even if the finger is removed from the switch 13 and the switch 13 is wrongly depressed again in this state, the electric current from the line flows to the TR 9 and the TR 15 does not operate. Accordingly, no current is made to flow to the coil 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention allows a telephone call to be made without lifting the handset from the telephone body. The present invention relates to a circuit for a telephone that performs so-called speakerphone calls.

(b) Prior Art Conventionally, the circuit shown in FIG. 2 has been used as a telephone circuit of this type. (1) is a tip, (1) is connected to a telephone line by a ring and is connected to a diode rectifier circuit (2),
Connected to the hook switch (3), the hook switch (3)
) is provided in parallel with a speakerphone changeover switch (4).

These switches connect speech network related circuits (5
) is connected to the speakerphone power switch (6),
Further, the switch (6) is connected to the base of a mode switching transistor (9) via a speakerphone related circuit (7) and a resistor (8). Note that when the transistor (9) is off, the communication mode is switched, and when it is on, the speakerphone mode is switched. The speech network related circuit (5) and the speakerphone related circuit (7) are connected by the signal line GOi QOI, and the collector of the mode switching transistor (9) is connected to the speech network related circuit (5) via the diode α1) f12. It is connected.

(13j is a speakerphone switch that remains on only as long as it is pressed with a finger, and is connected to the diode rectifier circuit (2) and also to the relay coil <141. The above-mentioned speakerphone changeover switch (4) And the speakerphone power switch (6) is connected to this relay coil (1ω
is configured to close in relation to.

This is a speakerphone transistor, the collector of which is connected to relay coil I, and the base of which is resistor uQ.

Connect the speakerphone switch (13) through the capacitor U71.
Connected to 1. Note that 08) and 0!3 are resistors, and the latter is a diode.

In this conventional circuit, when speakerphone switch 0J is turned on without lifting the handset (not shown), current from the telephone line flows through capacitor αη and resistor 0e to the base of transistor a9, turning on transistor 4. , current flows through the relay coil circle. This closes the speakerphone selector switch (4) and the speakerphone power switch (6), putting the telephone circuit into an off-hook state and making it possible to make a speakerphone call.

However, depending on the exchange, the line voltage rises slowly, and even if you keep pressing the speakerphone switch a3, sufficient current may not flow through the capacitor Q'7) to the base of the transistor mark, and the off-hook state may not occur. .

Furthermore, even if you keep pressing the speakerphone switch (13) after going off-hook, if the capacitor α'7) is charged, current will no longer flow through the base 1 of transistor 09, transistor 05) will be turned off, and the coil C
No current flows through 141. Considering this state I,
When the - degree switch (2) is released from the finger, the capacitor αη is discharged through the resistor 081.

Therefore, if you press the switch (2) by mistake next time, the coil 0Φ will be charged until the capacitor α is charged as described above.
Current flows through the tip (1) and the ring (1).
1) The impedance between the devices becomes low, making it difficult to communicate.

This is because the coil αa with an impedance of about 170Ω is connected in parallel with the telephone circuit ζ with an impedance of about 3000Ω, so the impedance is low, and the transmitting and receiving signals are bypassed by the coil (141 and transistor A).
This is due to insufficient current flowing through the speech network related circuit (5).

i/-1 Problems to be Solved by the Invention The present invention solves the above-mentioned problems, such as the fact that the off-hook state does not occur in exchanges where the line voltage rises slowly, and the problem that call failure occurs due to erroneous operation during a speakerphone call. This is to solve the problem.

4. Means for Solving the Problems The present invention provides a speakerphone switch, a relay coil connected to the switch, an off-hook switching switch and a speakerphone power switch associated with the coil, and a relay coil connected to the coil. The second transistor is connected to the base of the first transistor via a diode, and a resistor is connected between the speakerphone switch and the connection point between the base of the first transistor and the diode.

(e) Operation: Since current from the line flows through the base of the first transistor without passing through a capacitor, the first transistor operates reliably even if the line voltage of the exchange is slow to rise. Furthermore, the resistance connected between the speakerphone switch and the connection point between the base of the first transistor and the diode prevents the influence of the impedance of the relay coil from being affected in the event of an erroneous operation.

(F) EXAMPLE The present invention will be explained below with reference to FIG. FIG. 1 is a circuit diagram showing one embodiment of the present invention, and the same parts as in FIG. 2 are given the same numbers and the explanation will be omitted. In one embodiment of the present invention, the base of the transistor 05) is connected to the collector of the mode switching transistor (9) via the diode 2, and the connection point A between the base of the transistor α9 and the anode of the diode is connected to the speakerphone. A resistor is connected between the switches. Resistance (21) is approximately 6.8
The resistance value is more than 20 times the DC resistance of the entire telephone circuit (approximately 300Ω).

In this inventive circuit, when the speakerphone switch 0J is turned on without lifting the handset (not shown), current from the telephone line flows through the resistor αO to the base of the transistor 09. At this time, the transistor (9) is in an off state because the speakerphone power switch (6) is open.

Transistor (2) turns on even if the line voltage of the exchange is slow to rise, current flows through the relay coil, and the speakerphone changeover switch (41) and speakerphone power switch (6) close, resulting in an off-hook state. ( Note that both switches are opened only by the operation of a speakerphone off circuit (not shown). When the switch (6) is closed, the transistor (9) is turned on, pulling the diode υ■ to ground and at the same time also disconnecting the diode □□□. This causes the current supply to the base of transistor 09 to be cut off, turning off the transistor.

In this state, even if you take your finger off the switch OJ and press the switch αJ again by mistake, the current from the line will flow through the diode 1 to the transistor (9), so the transistor 19 will not operate and the coil 0 No current flows through Shinko.

Resistance CI again! Since the resistance value (R) of 1) is set to R≫r with respect to the DC resistance value frl of the entire telephone circuit, almost no current flows through the resistor (2), and even if switch 03 is pressed in the off-footer state, Sufficient current flows through the speech network related circuit (51) and does not interfere with speech communication.

(G) As described in detail, according to the present invention, speakerphone calls can be made reliably even in exchanges where line voltage rises slowly, and there is no possibility of erroneous operation during speakerphone calls. There will be no problem with the call.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a conventional circuit diagram. (4)...Speakerphone selector switch, (6)...
Speakerphone power switch, (9)...Mode switching transistor, (13)--Speakerphone switch,
0 phrase...Relay coil, Q5)...Speakerphone transistor, Cυ...Resistor, Prisoner...Diode.

Claims (2)

[Claims] (1) In a telephone circuit that can switch to off-hook mode (speakerphone call mode) by supplying line power by operating a switch, there is a speakerphone switch, a relay coil connected to the switch, and an off-hook switch related to the coil. a switch and a speakerphone power switch; a first transistor connected to the coil; a second transistor connected to the base of the first transistor via a diode; a base of the speakerphone switch and the first transistor; and a resistor connected between the connection points of the diodes, and when the speakerphone switch is turned on, the first transistor is operated and current flows through the relay coil to turn on the off-hook changeover switch and the speakerphone power switch. A telephone circuit characterized in that, after being turned on, the second transistor cuts off current supply to the first transistor. (2) The telephone circuit according to claim 1, wherein the resistance (R) is set in a relationship of R>>r with respect to the direct current resistance (r) of the entire telephone circuit.