JPS6163145A - Ring trip circuit - Google Patents

Abstract

PURPOSE:To obtain a stable ring trip characteristic by providing a circuit for outputting the voltage of the waveform the same as an input in the condition where both of them are electrically separated and a comparator with a far high input impedance in a current detection circuit so as to constitute an LPF having a low cut-off frequency. CONSTITUTION:When a telephone set 20 is in the on-hooked state, an AC voltage is produced at both ends of a ringer current detection resistance 2. When said voltage is in a positive half-cycle, a photocoupler 5a is conducted and a half-waveform is outputted to a load resistance 6a. Moreover, when the resistance 2 is in a negative half-cycle, a photocoupler 5b is conducted to output a half-waveform to a load resis tance 6b. Voltages of the resistances 6a and 6b are synthesized to the same voltage as both end voltages of the resistance 2 by means of conversion resistances 15a, 16a, 15b and 16b and a differential amplifier 17, cut by an LPF constituted of a resistance 3 and a capacitor 4, and a high potential signal is outputted from a comparator 9. When the telephone set is in the off-hooked state, a ringer relay is turned on, and the voltage equal to both end voltages of the resistance 2 is outputted from the ampli fier 17. Its DC component is transmitted to the comparator and a low potential signal is outputted from the comparator 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ring trip circuit used in a subscriber circuit of a telecommunications exchange.

[Conventional technology]

As shown in Fig. 3, the conventional ring trip circuit includes a ringer current limiting resistor 1, a ringer current detecting resistor 2 that converts the ringer current into voltage, and a DC voltage is obtained by integrating the output current of the resistor 2. Resistor 3 that makes up the low-pass filter
and a capacitor 4, an optical coupling element (hereinafter referred to as a photocoupler) 5, which electrically separates the output voltage of this low-pass filter and transmits a signal to the logic system, a photocoupler load resistor 6, and an output of the photocoupler. The comparator 9 converts the signal into a logic signal, and the resistors 7 and 8 set the dark value of the comparator 9.

As shown in FIG. 4, this circuit consists of a ringer relay 25a
and 25b, a telephone 20 including a hook switch 21, a DC blocking capacitor 22, and a bell coil 23, a ringer voltage generator 31, and a DC power source 32.

First, when the ringer relays 25a and 25b are on and the hook switch 21 is off (the telephone 20 is in the on-footer state), the ringer current flows through the ringer current detection resistor 2, the ringer relay 25a, and the direct!
An alternating current flows through the blocking capacitor 22, the bell coil 23, and the ringer current limiting resistor 1, and an alternating current is generated across the ringer current detecting resistor 2. However, if the cutoff frequency of the resistor 3 and capacitor 4 that make up the low-pass filter is set sufficiently lower than the frequency of the ringer voltage, sufficient voltage will not appear across the capacitor 4 and the output terminal 14 of the ring trip circuit No signal is sent from.

Next, when the hook switch 21 is turned on while the ringer relays 25a and 25b are in the on state (when the telephone 20 is in the off-footer state), the ringer voltage generator 31
The combined current of the AC current from the AC current and the DC current from the DC voltage 32 is applied to the ringer current detection resistor 2 and the ringer relay 25a.
The voltage flows through the single-hook switch 21, the ringer relay 25b, and the ringer current limiting resistor 1, and a composite voltage of the DC voltage and the AC voltage is generated across the ringer current detection resistor 2. The DC component of this voltage is filtered by a resistor 3 and a capacitor 4 that constitute a low-pass filter, and a photocoupler 5
A current calculated by dividing the direct current generated across the ringer current detection resistor 2 by the value of the low-pass filter resistor 3 flows on the primary side, and this current lowers the secondary output current of the photocoupler 5, and also reduces the output current of the photocoupler 5. 9 is also lowered and outputted from terminal 14 as a ring trip signal.

[Problems that the invention attempts to solve]

In the conventional ring trip circuit that operates in this manner, it is necessary to prevent the output of the ring trip signal when the telephone 20 is on-hook, and therefore the resistor 3 and capacitor 4 that constitute the low-pass filter each have a large value. Becomes an element of On the other hand, in order to facilitate the output of the ring trip signal when the telephone 20 is in the off-footer state, it is necessary to pass a large amount of DC current through the photocoupler 5, and the value of the resistor 3 forming the low-pass filter must be small. is desired. That is, conventional ring trip circuits require large components such as large capacity capacitors, and have the drawback of requiring large currents.

The present invention aims to eliminate such drawbacks, and provides an economical ring trip circuit with excellent characteristics and ease of implementation.

[Means for solving problems]

The present invention provides a conversion means (2) for converting ringer current into voltage.
As a means for solving the above-mentioned problem, a ring trip circuit including a separation circuit (5a, 5a, 5b, 6a, 6bS15a, 15
b, 16a, 16b, 17.18) and a filtering circuit (3, 4) that passes the DC component from the output means of this separation circuit.
and logic signal converting means (7, 8, 9) for outputting a logic signal according to the output of the filter circuit (3, 4).

[Effect]

When the telephone is in the on-footer state, only alternating current is supplied to the conversion means (2) and the filtering circuit (3, 4)
A high level signal is output from the logic signal conversion means (7, 8, 9).

On the other hand, when the telephone is off-hook, the conversion means (2
) is supplied with a composite current of alternating current and direct current, a direct current component is output from the filter circuit (3, 4), and a low level signal is output from the logic signal conversion means (7, 8, 9).

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A device according to an embodiment of the present invention will be explained below based on the drawings.

FIG. 1 is a block configuration diagram showing the configuration of the apparatus of this embodiment. FIG. 2 shows signal waveforms of each part of the apparatus of this embodiment, and is a waveform diagram illustrating the operation of the circuit of this embodiment when the telephone is on-hook and when the telephone is off-hook.

First, the configuration of this embodiment device will be explained based on FIG. This embodiment device includes a ringer current limiting resistor 1, a ringer current detecting resistor 2 that converts the ringer current into a voltage, photocouplers 5a and 5b that electrically separates and outputs the voltage across this resistor 2, and a photocoupler 5a and 5b that electrically separates and outputs the voltage across the resistor 2. Load resistors 6a and 6b of the coupler and a limiting resistor 18 that limits the photocoupler voltage
and a conversion resistor 15a that converts a balanced signal into an unbalanced signal.
, 15b, 16a and 16b, a differential amplifier 17, a filter resistor 3 and a filter capacitor 4 constituting a low-pass filter, a comparator 9, setting resistors 7 and 8 that determine the dark value of this comparator, and a telephone terminal. 10 and 11
, power terminals 12 and 13 , and an output terminal 14 .

A ringer current limiting resistor 1 is connected between a telephone terminal 11 and a power supply terminal 12. A ringer current detection resistor 2 is connected between the telephone terminal 10 and the power supply terminal 12.

Telephone terminal 10 is connected to photocoupler 5 via limiting resistor 18.
The anode of the photodiode section a and the photocoupler 5b
is connected to the cathode of the photodiode section of the photocoupler 5a, and the photocoupler 5a is connected to the cathode of the photodiode section of the photocoupler 5a.
The anode of the photodiode section b is connected to the power supply terminal 12.

The emitter of the transistor section of the photocoupler 5a is connected to a common potential via a load resistor 6a, and the emitter of the transistor section of the photocoupler 5b
The emitter of the transistor section is connected to a common potential via a load resistor 6b. Further, the emitter of the transistor section of the photocoupler 5a is connected to the positive input of the differential amplifier 17 via the conversion resistor 15a, and the connection point between the conversion resistor 15a and the positive input of the differential amplifier 17 is connected to one end of the conversion resistor 16a. The other end of the conversion resistor 16a is connected to the output of the differential amplifier 17. The emitter of the transistor section of the photocoupler 5b is connected to a common potential via the conversion resistor 15b and the conversion resistor 16b, and the connection point between the conversion resistor 15b and the conversion resistor 16b is connected to the negative input of the differential amplifier 17. The output of the differential amplifier 17 is connected to a common potential via a filter resistor 3 and a filter capacitor 4. The connection point between filter resistor 3 and filter capacitor 4 is connected to the negative input of comparator 9. The collector of the transistor section of the photocoupler 5a and the collector of the transistor section of the photocoupler 5b are connected to a common potential via a setting resistor 7 and a setting resistor 8, and the connection point between the setting resistor 7 and the setting 1 resistor 8 is compared. It is connected to the positive input of the device 9. The output of comparator 9 is connected to output terminal 14.

Next, the operation of this embodiment circuit will be explained based on FIGS. 1 and 2. This embodiment circuit is a telephone set 20 shown in FIG. Ringer relays 25a and 25b1 are connected to ringer voltage generator 16 and DC power supply 17.

First, when the telephone 20 is in the on-hook state, the ringer relays 25a and 25b are turned on, and only alternating current is supplied from the ringer voltage generator 31 to the ringer current detection resistor 2, and the voltage across the ringer current detection resistor 2 is changed to AC. A voltage is generated, and during a positive half cycle of this voltage, the photocoupler 5a is in a conductive state and a half wave waveform is output to the load resistor 6a. Further, during a half cycle in which the voltage of the ringer current detection resistor 2 is negative, the photocoupler 5b becomes conductive, and a half wave waveform is output to the load resistor 6b. The voltage output to the load resistors 6a and 6b is transferred to the conversion resistors 15a, 16a,
15b and 16b and a differential amplifier 17, the voltage is combined to the same voltage as the voltage across the ringer current detection resistor 2, and this combined voltage is cut by a low-pass filter consisting of a filter resistor 3 and a filter capacitor 4, and is output from a comparator 9. A high level signal is output.

Next, when the telephone 20 is in the off-hook state, the ringer relays 25a and 25b are turned on, and a voltage equal to the voltage across the ringer voltage detection resistor 2 is output from the differential amplifier 17 by the same operation as in the off-hook state described above. This voltage is passed through a low-pass filter consisting of a filter resistor 3 and a filter capacitor 4, and only the DC component is output. is output.

〔Effect of the invention〕

As explained above, the present invention provides the ringer current detection circuit of the ring trip circuit with a circuit that outputs a voltage with the same waveform as the input in an electrically isolated state and a comparator with extremely high human impedance. The resistance of the low-pass filter provided before the comparator may have a high resistance, so that a low-pass filter with a low cutoff frequency can be easily constructed. This provides the ring trip circuit with stable characteristics and has the effect of realizing a low-cost circuit configuration.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing the configuration of an embodiment circuit. FIG. 2 is a waveform diagram showing waveforms of various parts of the circuit of the embodiment; FIG. 3 is a block diagram showing the configuration of a conventional circuit. FIG. 4 is a connection diagram showing the relationship between the ring tri-71 circuit and peripheral circuits. DESCRIPTION OF SYMBOLS 1... Ringer current limiting resistor, 2... Ringer current detection resistor, 3... Filter resistor, 4... Filter capacitor, 5.5a, 5b-Photocoupler, 6.6a. 6b...Load resistance, 7.8...Setting resistance, 9...
Comparator 10.11...telephone terminal, 12.13...
Power supply terminal, 14... Output terminal, 15.15a, 1
5b, 16.16a, 16b - conversion resistor, 17.
... Differential amplifier, 18 ... Limiting resistor, 20 ... Telephone, 21 ... Hook switch, 22 ... DC blocking capacitor, 23 ... Bell coil, 25a, 25b.
... Ringer relay, 31 ... Ringer voltage generator, 32
...DC power supply. Patent applicant: NEC Corporation -1, agent: Naotaka Ide (patent attorney)

Claims (2)

[Claims] (1) In a ring trip circuit including a conversion means for converting a ringer current into a voltage, a separation circuit that is connected to the conversion means in an electrically separated state and outputs a voltage with a waveform equal to the waveform of this voltage; A ring trip circuit comprising: a filter circuit that passes a DC component from an output means of a separation circuit; and a logic signal converter that outputs a logic signal according to the output of the filter circuit. (2) The separation circuit includes two photocouplers connected in parallel to the output of the conversion means and with opposite polarities, and a differential amplifier that uses each output of the two photocouplers as two inputs. A ring trip circuit according to claim (1).