JPS6226616B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a press-to-talk type dial telephone, and particularly to control of direct current such as hook-on current and dial current.

FIG. 1 is a block wiring diagram showing an example of a conventional press-to-talk dial telephone. In the figure, 1 is the line current limiting resistor R ₁ , 2 is the dial contact, 3 is the hybrid transformer, 4 is the receiver, 5 is the balance circuit, 6 is the transmitter, 7 is the pre-talk switch, and 8 is the line holding resistor R ₂ , 9 is a closed contact when dialing, 10 is a hook switch, 11 is a telephone line
L ₁ and 12 are telephone lines L ₂ .

In the press-to-talk telephone configured as described above, when the switch 10 is raised, the contact closes and the current from the telephone line L ₁ 11 is passed through the line current limiting resistor 1, the dial contact 2, and the line holding resistor 8.
and telephone line L ₂ through the switch 10
It flows to 12. When a dial is made, the dial contact 9 closes and the dial contact 2 opens depending on the number of dials. That is, while the dial contact 2 is open, no current flows, resulting in a dial pulse as shown in FIG.

FIG. 2 is a current behavior diagram of a telephone line, where the vertical axis shows the current value and the horizontal axis shows time.

During press talk, when press talk switch 7 is pressed, a current determined by line current limiting resistor 1 flows through transmitter 6 as shown in FIG. However, in conventional press-to-talk type dial telephones, the dial pulse is sent in the form of a current interruption, so its detection requires a complex detection circuit, and furthermore, the hook current (holding current) is low even when the hook switch is raised. There were also momentary interruptions.

The object of the present invention is to provide a press-to-talk type dial telephone that allows a holding current to flow even during dialing without changing the mechanical parts of the conventional press-to-talk type dial telephone, and that allows easy detection of dial pulses. That is.

FIG. 3 is a block diagram showing an embodiment of the present invention, and 1 to 8 and 10 to 12 indicate the same or corresponding parts as the same reference numerals in FIG. 1 above.
In the figure, 20 is a transistor of the dial inversion circuit. FIG. 4 is a current behavior diagram of the telephone line of the embodiment of FIG.

In the press-to-talk type dial telephone configured as described above, when the hook switch 10 is raised, the contact closes, and the current from the telephone line L ₁ 11 is passed through the current limiting resistor 1, the dial contact 2, the line holding resistor 8, and the hook switch. 10 to telephone line L ₂ 12. In this case, since the dial contact 2 is closed between the emitter and base of the transistor 20 of the dial inversion circuit, no current flows to the collector, and the telephone line current is mainly controlled by the line holding resistor 8.

When dialing, the dial contact 2 is opened and the emitter and base of the transistor 20 of the dial inversion circuit are opened, so that a current flows from the emitter to the base, and a current multiplied by the transistor amplification factor flows to the collector. That is, as shown in FIG. 4, the current is reversed and a dial pulse current flows.

During a press talk call, when the press talk switch 7 is pressed, a current mainly determined by the line current limiting resistor 1 flows through the transmitter 6 as shown in FIG.

Although the description of the calling bell was omitted in the above embodiment, the combined use of a calling bell and the like is no different from that of a normal telephone.

As explained above, the present invention has the effect of making the detection circuit inexpensive and reducing malfunctions due to the generation of spurious pulses due to the simple configuration of adding a dial inverting circuit using transistors.

[Brief explanation of the drawing]

Fig. 1 is a block wiring diagram showing an example of a conventional press-to-talk type dial telephone, Fig. 2 is a current behavior diagram of the telephone line of the device shown in Fig. 1, and Fig. 3 is a block diagram showing an embodiment of the present invention. The wiring diagram, FIG. 4, is a current diagram of the telephone line of the device of FIG. In the figure, 1 is a line current limiting resistor, 2 is a dial contact, 6 is a transmitter, 7 is a press talk switch,
8 is a line holding resistor, 10 is a hook switch, 1
1 and 12 are telephone lines, and 20 is a transistor of a dial inversion circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A pre-talk switch is provided in series with the transmitter of the telephone, and when transmitting a call, the voltage between the telephone lines passes through the line current limiting resistor and the winding of the hybrid transformer, and the transmitter is connected to the transmitter. In a press-to-talk type dial telephone connected so as to be added to a series circuit of a closed contact of the above-mentioned pre-stalk switch, and a closed contact of the box switch, the line current limiting resistor and the winding of the hybrid transformer are A transistor connected between the connection point with the line and the connection point between the prestalk switch and the footswitch, and a line connected between the base of this transistor and the connection point between the prestalk switch and the footswitch. a holding resistor, comprising a dial contact connected between the base of the transistor and a connection point between the line current limiting resistor and the winding of the hybrid transformer; A press-to-talk type dial telephone characterized in that a current flows through the above-mentioned transistor.