JPS63110856A - Ringing trip circuit - Google Patents

Abstract

PURPOSE:To miniaturize a subscriber circuit being made easily into an integrated circuit by detecting an off-hook by means of comparing the voltage of the outgoing point of the call signal of a constant current with a reference voltage. CONSTITUTION:The impedance of a telephone set 8 is large at the time of a on-hook, while it is small at the time of a off-hook. Therefore, the output voltage Vout of the call signal of the constant current is large or small respectively. Accordingly, a comparator 3 can discriminate between an on-hook state and an off-hook state to some extent by comparing the output voltage Vout with the reference voltage Vth. Then, when the compared output signal of the comparator 3 shows the off-hook, a signal from a control circuit 4 is counted 5, and if the counted contents reaches a prescribed value, a logical part 6 decides it to be the off-hook, and switches and connects the contact 7' of a relay 7. On the switching and the connection of the contact 7' from the state shown in a figure, the transmission of the call signal is stopped, and the telephone set 8 is connected to the network 10 of an exchange through the contact 7' and a circuit 9 with a BSCH capability, and a channel between an originating telephone set is formed.

Description

[Detailed Description of the Invention] [Summary] Since the impedance of the telephone when off-hook is small, when a constant current ringing signal is sent out and the telephone goes off-hook in response to the ringing signal, the amplitude of the output voltage of the ringing signal is reduced. Become. This change in output voltage is detected by comparing it with a reference voltage, and when the same state remains for a predetermined period of mm, it is determined that the device is off-hook, and the transmission of the calling signal is stopped.

[Industrial application field]

The present invention sends a constant current ringing signal to an incoming telephone, detects that it goes off-hook in response to the ringing signal, and
The present invention relates to a ring trip circuit that stops sending out a calling signal.

If a ringing signal is sent to the incoming telephone through the subscriber circuit of the exchange and the telephone goes off-hook in response to the ringing signal,
The sending of the ringing signal is stopped, and the incoming telephone and outgoing telephone are connected via a network of exchanges.

It is desired to quickly and accurately detect off-hook in response to such a call signal.

[Conventional technology]

The subscriber circuit in the digital exchange is BOR3CH
It has a T function, and B is a power supply (Battery).
feed), ○ indicates overvoltage image g'Li (Overvo
ltage protection), R is for ringing, and S is for line monitoring.
vis 1on), C is code decoding (Codec),
H is 2-wire to 4-wire conversion (Hybrid), T is test (Te
sting).

FIG. 4 is a block diagram of a conventional example, in which 31 is a calling signal generator, 32, 37 is a resistor, 33 is a DC power supply, 34 is a low-pass filter, 35 is a comparator, 36 is a relay, 36', 36
” is a contact point, 38 is a telephone, 39 is BOR3CI (out of 7 functions, B (power supply), S (line monitoring), H (2 wires - 4
40 is an exchange network, and TIP and RING are terminals of subscriber circuits.

The relay 36 is connected via a route (not shown) by the call control signal.
operates, and the contacts 36'', 36'' are in the state shown. As a result, the calling signal generating section 31 generates a signal of, for example, 16Hz.
A ringing signal with an effective value of 75 V at a frequency of 32. It is sent to the telephone 38 through the contact 36°, and flows to the ground through the contact 36'' and the resistor 37.The DC voltage from the DC power supply 33 is superimposed on this calling signal, and the telephone 38 In this state, the telephone 38 is equivalent to a series circuit of a resistor R, a capacitor C, and an inductance L, and is in a high impedance state.

When the telephone 38 goes off-hook, it becomes equivalent to a circuit in which a low resistance is connected in parallel to a series circuit of RLC, and becomes a low impedance state. Therefore, since the impedance changes and the flowing current changes between the on-hook state and the off-hook state, off-hook detection can be performed by detecting this change in current as a voltage drop across the resistor 32.

FIG. 5 is an explanatory diagram of the operation, in which (a) is the voltage waveform across the resistor 320, (b) is the output waveform of the low-pass filter 34, and (C
) indicates the output of the comparator 35. Before going off-hook, since the impedance of the telephone 38 is large, the direct current from the direct current power supply 33 is also small, and the calling signal generating section 31
The calling signal current from the resistor 32 is also small, and the voltage generated across the resistor 32 becomes an alternating current voltage with a small amplitude biased by the direct current voltage Vdc from the direct current power supply 33, as shown in (a). Therefore, the output signal of the low-pass filter 34 becomes a DC component from which the AC component with small amplitude has been removed, as shown in [b], and becomes higher than the reference voltage vth. Comparator 35
Then, the output signal level of the low-pass filter 34 is equal to the reference voltage V
By being larger than t b (as shown in C1,
Outputs a low level signal. Thereby, relay 3
6 continues to operate, its contacts 36', 36''
A ringing signal is sent to telephone 38 via.

When telephone 38 goes off-hook in response to a ringing signal, the impedance of telephone 38 is reduced. Thereby, the DC power supply 3
3 increases, and the calling signal current from the calling signal generator 31 also increases, so the voltage generated across the resistor 32 has a waveform like the waveform after off-hook in (a) of FIG.
It becomes an alternating current component with a large amplitude. Therefore, the low pass filter 3
The output signal level of No. 4 gradually decreases to below the reference voltage vth. The comparator 35 outputs a high-level signal as shown in (C) when the output signal level of the low-pass filter 34 becomes equal to or lower than the reference voltage vth. The relay 36 is thereby restored, its contacts 36'', 36'' are switched, the transmission of the ringing signal is stopped, the telephone 38 is connected via the circuit 39 to the exchange network 40,
A communication path is established with the calling telephone.

The calling signal generating section 31 in the conventional example described above uses a transformer to boost the voltage to form a calling signal, and this transformer has a DC current from a DC power supply 33 superimposed on an AC calling signal. Since it flows, a large core is required to prevent magnetic saturation. Therefore, the structure for sending the calling signal becomes large. In addition, in order to prevent overcurrent during off-hook or ground fault, it is necessary to connect resistors 32 and 37 for current limiting.
2 is used for off-hook detection, and since these resistors 32 and 37 are large, with a capacity of several watts, it is also possible to miniaturize the structure of the ring trip and the transmission of the ring signal. It was difficult.

Therefore, we previously proposed a configuration in which a calling signal is sent from a constant current source. FIG. 6 shows its configuration, where 41 is a first constant current circuit that draws in current, 42 is a second constant current circuit that sends out current, and 43 is a signal that generates a signal with the period of the calling signal. 44 is a control circuit, 45 is an inverting driver,
46 is a non-inverting driver, 47 is a relay contact, 48 is a telephone set, 49 is a circuit having B5CH6 function, 50 is a network, and TIP and RING are terminals of a subscriber circuit.

“1” and “0” alternately from the signal source 43 at the cycle of the calling signal.
A signal is applied to the control circuit 44 by the call control signal, and a relay (not shown) is operated to close the contact 47.
When the signal from the signal source 43 is 1°, the constant current circuit 42 is driven by the output signal of the non-inverting driver 46 of the control circuit 44, and the constant current flows through the contact 47 due to the power supply voltage . When the signal from the signal source 43 is "0", the constant current circuit 41 is driven by the output signal of the inverting driver 45 of the control circuit 44, and the constant current is applied to the contact by the power supply voltage VSS. 47 from the telephone 48. Therefore, the first and second constant current circuits 41 and 42 operate alternately according to the signal from the signal source 43, and a constant current ringing signal is supplied to the telephone 48. It will be sent out.

According to this configuration, it is possible to send a calling signal without using a transformer, and it is also possible to omit a current limiting resistor.

[Problem that the invention seeks to solve]

In the conventional example shown in FIG. 4, as mentioned above, the calling signal generating section 31 uses a transformer or the like.
However, the configuration shown in FIG. 6 has the advantage that it can be made smaller because it does not require the use of such a transformer. However, even if the impedance changes when the telephone 48 changes from the on-hook state to the off-hook state, it cannot be detected as a voltage drop due to the resistor 32 in FIG. 4 because it is a constant current ringing signal. Become.

SUMMARY OF THE INVENTION An object of the present invention is to transmit a constant current ringing signal, detect off-hook of a telephone, and stop sending the ringing signal with a simple configuration.

[Means for solving problems]

The ring trip circuit of the present invention performs off-hook detection by comparing the voltage at the sending point of a constant current ringing signal with a reference voltage, and will be described with reference to FIG.

A subscriber telephone 8 connected to terminals TIP and RING via a subscriber line has a first constant current circuit 1 to which a power supply voltage VSS is applied to draw current, and a first constant current circuit 1 to which a power supply voltage VOO is applied to send out a current. A constant current calling signal is transmitted from the second constant current circuit 2 to the relay 7 under the control of the control circuit 4.
In the configuration in which the output voltage is sent out through the contact point 7°, the output voltage Vout at the connection point of the first and second constant current circuits 1.2,
A comparator 3 that compares the reference voltage vth and a comparator 3 when the amplitude of the output voltage Vout at the connection point becomes small.
A counting unit 5 starts counting signals from the control circuit 4 based on the comparison output signal of , and determines whether or not it is off-hook based on the count content of this counting unit 5. When it is determined that it is off-hook, the contact 7 of the relay 7 is activated. A logic section 6 is provided to perform the switching connection, and by switching the contact 7'',
At the same time as stopping the sending of the calling signal,
It is connected to an exchange network 10 via a six-function circuit 9.

[Effect]

Since the impedance of the telephone 8 when on-hook is large, the output voltage Vout of the constant current ringing signal becomes large,
Since the impedance of the telephone 8 during off-hook is small, the output voltage Vout of the constant current ringing signal is small. Therefore, by comparing the output voltage Vout and the reference voltage vth in the comparator 3, it is possible to identify to some extent whether the on-footer state or the off-hook state is present. Then, when the comparison output signal of the comparator 3 indicates off-hook, the signal from the control circuit 4 is counted by the counting section 5, and when the count reaches a predetermined value, the logic section 6 determines that it is off-hook and relays the signal. Switch connection of contact point 7° at 7° is performed. Since the contact 7'' is switched from the state shown in the figure, the transmission of the calling signal is stopped, and the telephone 8 is connected to the network 10 of the exchange via the contact 7' and the circuit 9 for the BSCH function, and the communication between the telephone and the calling telephone is A communication path is formed.

〔Example〕

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

FIG. 2 is a block diagram of an embodiment of the present invention, in which 11 is a first constant current circuit, 12 is a second constant current circuit, 13 is a comparator, 14 is a control circuit, 15 is an inverting driver, and 16 is a 17.20 is a non-inverting driver; 17.20 is an AND circuit; 18 is a signal source that outputs a signal with the cycle of the calling signal; 19 is a shift register forming the counting section 5; 21.22 is an AND circuit 20
23 is an amplifier, 24 is a relay, 25 is a contact thereof, 26 is a telephone,
TIP and RING are terminals. The control circuit 4 in FIG. 1 includes the control circuit 14 and the signal processor 8.

The first constant current circuit 11 to which the power supply voltage VSS is applied
and power supply voltage ■. . The comparator 13 compares the output voltage Vout at the connection point with the second constant current circuit 12 to which the constant current circuit 12 is applied and the reference voltage vth, and the comparison output signal is applied to the clear terminal CL of the shift register 19. Further, the signal from the signal source 18 is applied to the clock terminal CK of the shift register 19, the clock terminal GK of the flip-flop 22, and the AND circuit 17.

When sending a ringing signal to an incoming telephone, the ringing control signal SD is “0”;
is applied to the data terminal of the flip-flop 22 and the set terminal S of the flip-flop knob 21, and the Q terminal output signal of the flip-flop 22 is applied to the data terminal of the shift register 19 and the AND circuit 17. The d-terminal output signal of the amplifier 22 is amplified by an amplifier 23 and applied to a relay 24. d of flip-flop 22
When the terminal output signal is "1", the relay 24 is in operation, and its contact 25 is switched to the opposite side as shown.

When the paging control signal SD becomes "0", the flip-flop 21 is set and its Q terminal output signal becomes "1", and the flip-flop 22 is set according to the timing of the signal from the signal source 18, and its d terminal output signal becomes "1". The output signal becomes "0". Therefore, the relay 24 is restored and its contact 25 is switched to the state shown in the figure. Also, the Q terminal output signal of the flip-flop 22 becomes "1", and the shift register 19's output signal becomes "1". “1” is added to the data terminal, and the signal source 18
The signals from Ql, Q2 . When all the Q3 terminal output signals become 1'', the output signal of the AND circuit 20 becomes 1'', and the flip-flop 21 is reset. Also, AND circuit 1
A signal from a signal source 18 is applied to the control circuit 14 via 7.

When the signal from the signal source 18 is 0'', the inverting driver 15
The first constant current circuit 11 is driven by the output signal, and a constant current is drawn.

Further, when the signal is "1", the second constant current circuit 12 is driven by the output signal of the non-inverting driver 16, and a constant current is sent out. Therefore, a constant current calling signal in the positive and negative directions is sent to the telephone 26 via the contact 25.

At the time of on-footer, the impedance of the telephone 26 is large, so the output voltage Vout, which is the product of the impedance, a composite impedance including the impedance of the subscriber line, and the constant current, has a large amplitude between the power supply voltages VsSr and VDII, for example. Let the reference voltage vth be 'J o o
＞ Q ＞ 'J th ＞ V s s The relationship between the output voltage Vout and the reference voltage vt is set.
By comparing the signal h with the comparator 13, the comparison output signal becomes "0" and "1" of the calling signal period. And “O
” is the clear terminal C of the shift register 19.
When added to L and cleared, QI+ Q2+ Q
All three terminal output signals become "0". Therefore, the output signal of the AND circuit 20 continues to be 0'', and the flip-flop 2
1, the set state continues.

Furthermore, when the telephone is off-hook, the impedance of the telephone 26 is reduced, so the amplitude of the output voltage Vout is also reduced.

As a result, the comparison output signal of the comparator 13 becomes "L" continuously, so that the shift register 19 is not cleared. Therefore, 1 in shift register 19
'' shift is performed, and when the Ql, Q2, and Q3 terminal output signals all become "L", the output signal of the AND circuit 20 becomes "1".
", and the flip-flop 21 is reset. As a result, the flip-flop 22 is cleared, and the output signal from this terminal becomes "1", the relay 24 is operated, and its contact 25 is switched and connected to the opposite side as shown in the figure. In addition, since the Q terminal output signal of the flip-flop 22 becomes "0", the signal from the signal source 18 is not applied to the control circuit 14 (the transmission of the ringing signal is stopped, and the telephone 26
is connected to the exchange network via a BSCH function circuit (not shown).

FIG. 3 is an explanatory diagram of the operation of the embodiment of the present invention, in which (a) shows the signal from the signal source 18, (b) shows the call control signal SD, (
C) is the operation and recovery of the relay 24, +d) is the output voltage V
o u t , (e) is the comparison output signal of the comparator 13, (
f).

(along, (h) is Q of shift register 19, ,Q2.Q3
The terminal output signal, +11 is the output signal of the AND circuit 20, (
Jl is the Q terminal output signal of the flip-flop 21.

At time 10, when the paging control signal SD becomes "O" as shown in (b), the flip-flop 22 is set according to the timing of the signal from the signal source 18, and the relay 2
4 is restored at time t1 as shown in (C), and its contact 2
5 is switched and connected to the state shown in FIG. Also, control circuit 1
4, the constant current circuits 11 and 12 are alternately controlled and a constant current calling signal is sent out. The output voltage Vout has an amplitude between the power supply voltages Vast and voo, as shown by (dl).

That is, due to the large impedance, the output voltage V
Even if out tries to increase, the power supply voltage VSS+
It is clamped to VDD and does not increase any higher than that, and the maximum power supply voltage is V3! + voo.

When the reference voltage vth is set as shown in the figure, the comparison output signal of the comparator 13 becomes " when the output voltage Vout is at a level close to the power supply voltage VS3, as shown in (e).
0". Therefore, the shift register 19 is cleared by this comparison output signal of "0", so the Q1 terminal output signal of the shift register 19 becomes a pulse as shown in (fl), and the other Q2, Q3 The terminal output signal becomes "0".

When the phone goes off-hook at time t2, the impedance of the telephone becomes small, the amplitude of the output voltage Vout becomes small, and Vout>Q. Therefore, since Vout>Vth, the comparison output signal of the comparator 13 becomes a continuous "1". Become. Therefore, since the shift register 19 is not cleared, the "1" signal applied to the data terminal is shifted, and as shown in (f), (gl, (h)), Q, .
Q2. All Q3 terminal outputs become "1" at time t3, and the output signal of the AND circuit 20 becomes "1" as shown in (1).
” becomes.

Since this "1" signal is applied to the reset terminal R of the flip-flop 21, the flip-flop 21 is reset, and as shown in (j), its Q terminal output signal becomes "
0”, and this “0” signal clears the clear terminal CL.
Flip-flop 22 applied to
It is operated as shown in C), and the contact 25 is switched and connected to the side opposite to that shown.

Furthermore, since the flip-flop 22 is cleared, its Q terminal output signal becomes "0", the AND circuit 17 is closed, and no signal is applied from the signal source 18 to the control circuit 14. Therefore, sending out the calling signal by constant current is stopped. Further, by switching the contact 25 of the relay 24, the telephone 26 is connected to the exchange network via a BSCH function circuit (not shown).

The relationship between the operation and restoration of the relay 24 and the sending and stopping of the calling signal may be reversed from the above-described embodiments in consideration of the control of the relay 24. That is, it is also possible to adopt a control configuration in which the relay 24 is activated to send out the calling signal, and the relay 24 is restored to stop the calling signal.

Of course, it is also possible to use a normal counter as the shift register 19. Further, the predetermined count number can be selected depending on the relationship between the cycle of the clock signal and the ring trip time.

〔Effect of the invention〕

As explained above, the present invention utilizes the fact that, in a configuration that sends out a constant current calling signal, the output voltage changes between on-footer and off-hook to respond to the calling signal. It detects off-hook, and since the counting section 5 and the logic section 6 can be constructed of digital circuits, it is easy to integrate the circuit, and there is an advantage that the subscriber circuit can be miniaturized. .

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is an explanatory diagram of the operation of the embodiment of the invention, Fig. 4 is a block diagram of a conventional example, and Fig. 5 is a block diagram of the principle of the present invention. The figure is an explanatory diagram of the operation of the conventional example, and FIG. 6 is an explanatory diagram of the conventional example. 1 is a first constant current circuit, 2 is a second constant current circuit, 3 is a comparator, 4 is a control circuit, 5 is a count section, 6 is a logic section, 7
is a relay, 7° is a contact, 8 is a telephone, 9 is a BSCH function circuit, 10 is a network, 11 is a first constant current circuit, 12 is a second constant current circuit, 13 is a comparator, 14 is a control circuit , 15 is an inverting driver, 16 is a non-inverting driver, 1
7 is an AND circuit, 18 is a signal source, 19 is a shift register, 20 is an AND circuit, 21, 22 is a flip-flop, 23 is an amplifier, 24 is a relay, 25 is a contact, and 26 is a telephone set. Fig. 1 Block diagram of the embodiment of the present invention Fig. 2 An explanatory diagram of the operation of the embodiment of this research Block diagram of the conventional example An explanatory diagram of the operation of the conventional example Fig. 5 An explanatory diagram of the conventional example Figure 6

Claims (1)

[Claims] A first constant current circuit (1) that draws current and a second constant current circuit (2) that sends out current are operated alternately by a control circuit (4) to create a relay. (7) Contact (7')
In a configuration in which a constant current calling signal is sent to the subscriber telephone (8) via the first and second constant current circuits (1
), a comparator (3) that compares the output voltage at the connection point of (2) with a reference voltage, and a comparator (3) that compares the output voltage at the connection point of (2) with the reference voltage;
), a counting section (5) that starts counting signals from the control circuit (4) and the count contents of the counting section (5) are identified to determine whether or not the off-hook condition is detected. A ring trip circuit comprising: a logic unit (6) that switches and connects a contact (7') of the relay (7) to stop sending out the ring signal when it is determined that the ring trip circuit has a ring trip circuit.