JPS62239649A - Telephone set provided with automatic holding release fucnction - Google Patents

Abstract

PURPOSE:To facilitate the transfer of talking by using an electronic switch to hold a DC loop at holding and detecting the closing of the DC loop by other telephone set in branch connection to the same line thereby releasing the holding state automatically. CONSTITUTION:A capacitor 17 is charged through a resistor 15 and a diode 16 at on-hook holding state. In forming the branch state, a current flowing to a closed DC loop is reduced and the line voltage is decreased. When the voltage at the anode side of the diode 16 is lowered, the electric charge charged in the capacitor 17 is discharged through the emitter and base of a transistor (TR) 20, which is turned on and the electric charge in the capacitor 17 turns on a TR 26 through a resistor 24. When the TR 26 is turned on, a signal of H L is caused at a terminal 13b and the signal becomes a holding reset signal.

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention provides a method for using a plurality of telephones in a branch connection to the same communication line, and when one telephone is in a hold state, the telephone in the hold state is This invention relates to a telephone that has a function to release the hold by opening the DC loop of the telephone.

(Prior Art and its Problems) Conventionally, the DC loop of a telephone with a hold function in the hold state has been held by a mechanical contact. Therefore,
When multiple telephones are connected to the same line and you want to make a call on another telephone after putting it on hold with one telephone, the telephone that is on hold after closing the DC loop with the other telephone This was extremely inconvenient as the user had to operate the system to release the hold.

(Purpose of the Invention) The present invention provides that when a plurality of telephones are branch-connected to the same communication line, when one telephone is on hold, the other telephones close the DC loop. To provide a telephone having a function of automatically opening a DC loop of a telephone in a hold state and releasing the telephone from hold.

(Structure of the Invention) For this purpose, a circuit configuration is adopted in which the DC loop in the hold state is maintained closed using an electronic switch, and a branch state detection circuit is provided which generates a detection output when the DC voltage of the telephone circuit drops by a certain value or more. The present invention is characterized in that it is configured to release the pending state based on the detection outputs of the two detection circuits.

The present invention will be explained in detail below with reference to the drawings.

(Embodiment) Fig. 1 shows an embodiment of the present invention, in which Ll and L2 are connecting terminals to the office line, 1 is a rectifier circuit, 2 is a DC loop closing circuit, 2a is a hook inch, 2b, 2G is a transistor,
2d and 2e are resistors, 3 is a communication circuit, 3a is an output terminal of a constant voltage source in the communication circuit, 3b is an external input terminal for sending hold music, etc. to the line, 4 is a power-on reset circuit, 5
is an AND gate, 6 is a flip-flop circuit, 7 is a resistor, 8 is a hold switch, 9 is a chattering removal circuit, 10
11 is a resistor, 12 is a transistor 12 is a hold tone generation circuit, 1
2a is a hold music output terminal, 13 is a branch state detection circuit, 13a is a line voltage input terminal, 13b is a branch state detection signal output terminal, and 14 is a resistor.

Here, the hook switch 2a in the DC loop closing circuit 2
goes off-hook, (L, -1-2→3 = 1-L
The DC loop is closed along the route x) and captures the central line. As a result, the power-on reset circuit 4 is connected to the terminal 3a.
The flip-flop circuit 6 is reset through the AND gate 5, and the Q output of the flip-flop circuit 6 becomes "L" and the Q-output becomes "H".

Therefore, when the hold switch 8 is turned on, an H-L signal is sent to the CK of the flip-flop circuit 6 through the chattering prevention circuit 9, and the Q output of the flip-flop circuit 6 becomes "H" and the hundred output becomes "L". In addition, the Q output of the flip-flop circuit 6 turns on the transistors 2c and 2d, so the DC loop is maintained regardless of whether the hook switch 2a is on or off. According to the transistor 11
is turned on, power is supplied to the hold music generation circuit 12,
The hold music is sent to the line through terminals 12a and 3b,
When the hook switch 2a is turned on-hook, the on-footer is placed in a suspended state.

Here, by off-hooking another similarly configured telephone (not shown) connected to L and Lz, it enters a branch state, and the branch state detection circuit 13 detects the branch state and outputs a signal from the terminal 13b. A reset signal is sent to the flip-flop circuit 6 through the AND gate 5.

Upon receiving the reset signal, the Q output of the flip-flop circuit 6 is restored to "L", and the 100 output is restored to "H", and this Q output turns off the transistor 11, and the held tone generation circuit 12 stops generating the held tone, and the transistor 2b .

By also turning off hook switch 2c, the DC loop is opened since hook switch 2a is on-hook.

FIG. 2 shows a specific example of the branch state detection circuit 13,
15.1B, 24.25 is a resistor, 16 is a diode,
17 and 19 are capacitors, and 20.26 is a transistor. In the above-described on-footer hold state, the capacitor 17 is charged through the resistor 15 and the diode 16. If a branch state is established here, the current flowing through the closed DC loop decreases, and the line voltage decreases. As a result, the voltage on the anode side of the diode 16 decreases,
The charge stored in diode 17 is transferred to transistor 2.
Discharging through the emitter base of 0 turns on transistor 20 and the charge on capacitor 17 passes through resistor 24 causing transistor 26 to turn on. Since the transistor 26 is turned on, the terminal 13b
An H-L signal is generated, and this signal becomes a pending reset signal.

(Effects of the Invention) As explained above, the telephone of the present invention uses an electronic switch to maintain the DC loop when on hold, and detects that another telephone branch-connected to the same line has closed the DC loop. Since the telephone is configured to automatically release the hold state when the call is on hold, it has the advantage that it can be automatically released from the hold state and calls can be transferred extremely easily.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a branch state detection circuit used in the present invention. L+, Lx... line terminal, 1... rectifier circuit, 2...
...DC loop closing circuit, 2a... Hook switch, 2b, 2c, 11.20.26... Transistor, 2d, 2e... Resistor, 3... Call circuit, 3a,
3b...terminal, 4...power-on reset circuit,
5...AND gate, 6...Flip-flop circuit, ? , 10.14.15.18.24.2
5...Resistor, 8...Switch, 9...Chattering removal circuit, 12...Hold tone generation circuit, 13.
...Branch state detection circuit, 13a, 13b...terminals, 16...diode, 17.19...capacitor.

Claims (1)

[Claims] A hold key, a hold state control flip-flop circuit that performs a toggle operation by inputting press information of the hold key, an electronic switch that maintains a DC loop by the output of the flip-flop circuit, and a constant voltage across the call circuit. The present invention is characterized by comprising a branch state detection circuit that generates a detection output when the branch state detection circuit decreases by more than a value, and a circuit that resets the holding state control flip-flop circuit and releases the holding state based on the detection output of the branch state detection circuit. A telephone with an automatic hold release function.