JPS5916457B2 - starting circuit - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a starting circuit used in, for example, automatic telephone answering equipment, etc., and is particularly designed to prevent the equipment from being erroneously started due to interference noise such as dialing signals. It is.

Conventional startup circuits of this type include a rectifier that rectifies the signal from the telephone line, a capacitor that integrates the rectified output, and a Schmitt trigger circuit that turns on when the terminal voltage of this capacitor rises above a certain level. It consists of a switching circuit.

Therefore, the conventional activation circuit has the disadvantage that, regardless of the nature of the incoming signal, the activation circuit is energized by, for example, a dial signal, thereby erroneously closing the line.
This invention aims to correct the above-mentioned drawbacks, and its purpose is to reliably distinguish between a bell signal and a dial signal by integrating the input pulse once shaped by a waveform shaping circuit. An object of the present invention is to provide a starting circuit which can further improve the reliability of equipment.

Embodiments of the present invention will be described below with reference to the drawings.

That is, in the figure, IN is an input terminal connected to a telephone line, and R3 and C3 are its input resistance and capacitor. T is a line transformer, the secondary side of which is connected to the base of the transistor Q4 via a resistor R3, and to the emitter of the transistor Q3 via a parallel circuit of a resistor R2 and a capacitor C2. The collector of the transistor Q4 is connected to the base of the transistor Q4 via a resistor R4, and is also connected to a monostable multivibrator (waveform shaping circuit) consisting of transistors Q2, Q3, resistors R|-R8, and a capacitor C3. The emitter of the transistor Q4 is connected to the power supply +B, and its collector has a variable resistor VR.
An integrating circuit made up of a capacitor C4 is connected through the capacitor C4. A differentiating circuit consisting of a capacitor C5 and a resistor R9 is connected to this integrating circuit, and a first switch circuit consisting of resistors R0o-R02 and Darlington-connected transistors Q3 and Q6 is connected to this differentiating circuit. . Transistor Q in this first switch circuit
6 is connected to the integrating circuit through the resistor R32, and therefore, when the differential value of the output in the integrating circuit is zero or close to zero, the transistor Q6 is turned on.
It operates to reset the output of the integration circuit to zero. In addition, the above integration circuit includes a zener diode Z.
D) A second switch circuit consisting of a resistor R18 and a transistor Q7 is connected, and the transistor Q is turned on when the terminal voltage of the capacitor C4 forming the integration circuit rises above the breakdown voltage of the Zener diode ZD. It operates as follows. The above transistor Q,
A collector resistor Rl4 is connected to the collector between the power source 1B and a time constant circuit consisting of a variable resistor VR2 and a capacitor C6 is connected to both ends of the collector resistor Rl4. The cathode of a diode D is connected to the connection point between the variable resistor VR and the capacitor C6, and the start signal output terminal 0UT is connected to the anode of the diode D.
is provided. Therefore, for example, when a bell signal, dial pulse, etc. arrives at the input terminal, the transistor Q is turned on and off via the line transformer T.

Since a monostable multivibrator is connected to the collector of this transistor Q1, all input pulses are waveform-shaped into pulses of a specific width based on the time constant of this monostable multivibrator, and then are passed through the transistor α. It will be brought to the base. Therefore, the capacitor C4 connected to the collector of this transistor Q4 is charged with a voltage proportional to the number of input pulses. As is well known, the bell signal is a signal that is sent out at 16 Hz for one second, paused for two seconds, and then regenerated and sent out a signal at 16 Hz for one second. The number of arriving pulse groups is 10 or less. Therefore, for example, when a dial pulse arrives at the input terminal, the terminal voltage of the capacitor C4 does not rise to the breakdown voltage of the Zener diode ZD, and the first switch circuit turns on during the pause period of the dial pulse.
The voltage at the terminals of capacitor C4 will be set to zero, ie, grounded. That is, no matter how many times the dial pulse arrives, its integral value does not rise to a predetermined value, and all are set to zero during the rest period, so that the operation leading to activation is interrupted here. On the other hand, when a bell signal arrives at the input terminal, the capacitor C4 is charged with a voltage corresponding to the number of 16 pulses, so the Zener diode ZD is turned on and the transistor Q is also turned on.
During the rest period, the capacitor C
The terminal voltage of 4 is set to zero by the first switch circuit, but when the 16 Hz signal arrives again 2 seconds later, the zener diode ZD is turned on again, and the transistors Q,
will be turned on as well. That is, each time a 16 Hz bell signal arrives, the transistor Q is turned on, and therefore the capacitor C6 is repeatedly charged via the variable resistor V. Therefore, the potential of the output terminal 0UT decreases every time a bell signal arrives, and the telephone line can be configured to be closed using the output of the output terminal 0UT. As described above, the present invention is configured so that the input pulse is shaped into a constant pulse width and then integrated, and a start signal is generated according to this integrated value, so that it is possible to reliably distinguish between a dial pulse and a bell signal. Therefore, the intended purpose of the invention described at the beginning can be fully achieved. The activation circuit of the present invention can be used not only for automatic telephone answering devices, but also for key telephones activated by a bell signal, telex and facsimile devices, etc. with the same effect.

[Brief explanation of drawings]

The drawing is a circuit diagram showing an embodiment of the present invention. Q,,Q3...Transistor (waveform shaping circuit)
, R5 to R8...Resistor (waveform shaping circuit), C,
...Capacitor (waveform shaping circuit), C4...
... Capacitor (integrator circuit), VRl ... Variable resistor (integrator circuit), Q,, Q6 ...... Transistor (first switch circuit input R, ~Rl, ...・・・
・Resistor (first switch circuit), C, ... capacitor (first switch circuit), ZD ... Zener diode (second switch circuit), Rll ...
-Resistance (second switch circuit), Q,...transistor (second switch circuit).

Claims (1)

[Claims] 1 When a signal from a telephone line is input, the input signal is used as a trigger to shape it into a pulse of a constant width regardless of the width of the input signal, and the pulse signal shaped to a constant width is integrated to calculate the pulse signal. Obtain an output voltage corresponding to the number of input pulses regardless of the width of the input pulse, generate a start signal when the output voltage exceeds a predetermined value, and change the output voltage by differentiating the output voltage. 1. A start-up circuit characterized in that the output voltage is reset to zero when the rate of change is detected and the rate of change is less than a predetermined value.