JPH0241942B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ring trip system, and more particularly to a ring trip system in a ring signal sending circuit of a telephone exchange.

FIG. 1 is a diagram showing an example of a conventional ring trip method of a calling signal sending circuit. In FIG. 1, a ring signal current ir is supplied from a ring signal power source 1 via resistors 2 and 7 and a DC power source 6 to a telephone 5 connected to terminals 3 and 4, causing a bell to ring. Since a capacitor is inserted in the bell circuit of the telephone 5, the DC power supply ID is not sent out from the DC power supply 6 unless the subscriber responds.
In such a state, only an alternating current voltage due to the ringing signal current ir is generated across the resistor 7, and is blocked by the low-frequency wave generator composed of the resistor 8 and the capacitor 9, so that the transistor 11 is not energized. When the called party answers in such a state, the telephone 5
Since the bell circuit is removed and a DC loop circuit is formed, the DC power supply id flows superimposed on the ringing signal current ir, and a DC voltage is generated at both ends of the resistor 7 along with the AC voltage. When the capacitor 9 is charged by the DC voltage and the terminal voltage of the capacitor 9 exceeds the breakdown voltage of the voltage regulator diode 12, the transistor 11 is energized and the relay 13 is operated.
Contact 13' sends out a ring trip signal RTO from terminal 14 to notify a processing device or the like of the called party's response in a known manner.

As is clear from the above explanation, in the conventional ring trip method, a low frequency filter using a large capacitor is used to detect the direct current that flows superimposed on the ringing signal current ir when the called party answers. This results in hindering miniaturization of the calling signal sending circuit using LSI technology or the like.

An object of the present invention is to eliminate the drawbacks of the conventional ring trip method as described above, and to realize a ring trip method that can be realized by LSI technology without using large parts.

The purpose of this is to compare the ringing signal current sent by the ringing signal sending circuit with a predetermined reference value in the ringing signal sending circuit of the telephone exchange, and set a logic value of 1 during a period when the ringing signal current is determined to be greater than or equal to the reference value. , a comparison circuit that outputs a logical value of 0 outside the period, a delay circuit that delays the output of the comparison circuit by a half period of the calling signal current, and an AND of the output of the delay circuit and the output of the comparison circuit. This is achieved by providing a gate that outputs a signal, and detecting the direct current superimposed on the calling signal current using the output of the gate.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. FIG. 2 is a diagram showing a ring trip system according to an embodiment of the present invention in a calling signal sending circuit, and FIG. 3 is a diagram illustrating the operation sequence in FIG. 2. Note that the same reference numerals indicate the same objects throughout the figures. 2, until the called party answers, the telephone 5 connected to terminals 3 and 4 has a period T as shown in FIG.
Only the ringing signal current IR is supplied. The comparison circuit CMP, which is composed of operational amplifiers 15 and 16 and resistors 17 to 20, compares the AC voltage generated across the resistor 2 by the ringing signal current ir with a predetermined value, for example, 0 volts as a reference value, and compares the AC voltage The comparator circuit output RTP is set to a logic value of 1 during a period when the AC voltage is 0 volts or more, and the comparator circuit output RTP is set to a logic value of 0 during a period when the AC voltage is 0 volts or less. Therefore, the comparator circuit output RTP _is a logical value at the half period T/ ₂ in which the ringing signal current ir is positive at times t1 to t6 in FIG. 3, that is, at times _t1 to _t2 and _t3 to _t4 . 1 and the ringing signal current is set to half period T/2 during which ir is negative, i.e. at time t ₂
Comparison circuit output RTP from t ₃ to t ₄ to t ₅
is set to a logical value of zero. However, when the called party answers at time _t6 , the telephone 5 is supplied with the direct current id superimposed on the ringing signal current ir. Note that due to the decrease in the internal impedance of the telephone 5 due to the response, the ringing signal current ir itself also increases (see FIG. 3). As a result, the comparator circuit CMP compares the voltage generated across the resistor 2 due to the ringing signal current ir and DC current id, which have increased after time _t6 , with the reference value 0 volts for a period longer than half the period T/2 of the ringing signal current ir. , that is, the comparison circuit output RTP is set to a logical value 1 at times t ₅ to t ₇ , t ₈ to t ₉ and t ₁₀ to t ₁₁ , and conversely, during a period shorter than the first half cycle T/2, that is, from time t ₇ to t 11. Set to logical 0 at t ₈ and from t ₉ to t ₁₀ . The comparison circuit output RTP is synchronized with the clock signal CL by the flip-flop 23 and then transmitted to the delay circuit 24 and the gate 25. The delay circuit 24 provides a delay time corresponding to a half period T/2 of the calling signal current ir to the comparison circuit output RTP, and outputs a delayed output RTD. Therefore, the delayed output RTD is output at the time points t ₁ to t ₂ , t ₃ to t ₄ , t ₅ to t ₇ , t ₈ as shown in FIG.
Time t ₁ ′ to t ₂ ′, t ₃ ′ to t ₄ ′, t ₅ ′ to t ₇ ′, t ₈ ′ delayed by half period T/ ₂ from t ₉ and t 10 to t ₁₁
~
It is set to a logic value of 1 from t ₉ ' and t ₁₀ ' to t ₁₁ ' (not shown), and is set to a logic value of 0 at other times. The delayed output RTD is input to the gate 25,
An AND operation is performed with the comparison circuit output RTP. When the called party answers, before t ₆ , the RTP pulse
Since the duty is 50%, time t ₁ ′ is t ₂ and t ₂ ′ is
t ₃ and t ₃ ' approximately coincide with t ₄ and t ₄ ' approximately coincide with t ₅ , and the AND output RTA from the gate 25 is set to a logical value of 0, but after the above-mentioned time t ₆ , , point in time
t ₅ ′ to t ₇ , t ₈ to t ₇ ′, t ₈ ′ to t ₉ , t ₁₀ to t ₉ ′,
Then, from t ₁₀ ' to t ₁₁ , the AND output RTA is set to a logic value of 1. The logical AND output RTA is controlled by a correction circuit consisting of a delay circuit 26 having a delay time Td and a gate 27 to compensate for the fluctuation of the reference value 0 volt in the comparator circuit CMP or the flip-flop 2.
Comparison circuit output RTP due to synchronization in 3
Due to the temporal variation of , spurious outputs less than the pulse width Td occurring before the response time t ₆ are eliminated. The ring trip output RTO output by the correction circuit is transmitted from the terminal 28 to a processing device or the like to notify the called party of the response.

As is clear from the above description, according to this embodiment, the comparison circuit CMP, the delay circuit 24, the correction circuit, etc. can all be mounted at high density without using large components such as large capacity capacitors.

It should be noted that FIGS. 2 and 3 are only one embodiment of the present invention. For example, as a means for more reliably identifying the response of the called party, a counter 29 may be installed at the terminal 28 as shown in FIG. and a sequential judgment circuit 31, the counter 29 counts the number of outputs of the ring trip output RTO, and the sequential judgment circuit 31 outputs a response detection output that judges that the counted output 30 exceeds a predetermined reference value. It is also considered to transmit the RTQ (logic 1) to a processing device, etc., but the effects of the present invention do not change even in such a case. Further, the configurations of the comparison circuit CMP, the comparison circuit 24, and the correction circuit are not limited to those shown in the drawings, and many other modifications may be considered, but the effects of the present invention will not change in any case. Furthermore, the waveforms of the ringing signal current ir and the DC current id are not limited to those shown in the drawings, and may vary depending on the conditions of the line connecting the telephone 5, etc., but the effects of the present invention do not change in any case. . Furthermore, it goes without saying that the device that receives the calling signal is not limited to a telephone.

As described above, according to the present invention, it is possible to realize a ring trip method that does not require the use of large parts.
In addition to making it possible to miniaturize and high-density packaging the ringing signal circuits of telephone exchanges, it also has a configuration that allows for integrated circuits because the desired functions can be achieved using only comparison circuits and logic circuits. LSI technology also allows configuration on a single integrated circuit.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a conventional ring trip method for a calling signal sending circuit, FIG. 2 is a diagram showing a ring trip method according to an embodiment of the present invention in a calling signal sending circuit, and FIG. 3 is an operation in FIG. 2. FIG. 3 is a diagram illustrating a sequence. In the figure, 1 is a calling signal power supply, 2, 7, 8,
10, 17 to 20 are resistors, 3, 4, 14 and 28 are terminals, 5 is a telephone, 6 is a DC power supply, 9 is a capacitor, 11 is a transistor, 12 is a constant voltage diode, 13 is a relay, 13' is a contact, 15 and 16 are operational amplifiers, 23 is a flip-flop, 24 and 26 are delay circuits, 25 and 27
is a gate, CMP is a comparison circuit, 29 is a counter, 3
1 is a sequential judgment circuit, ir is a calling signal current, id is a direct current, RTP is a comparison circuit output, RTD is a delay output,
RTA is AND output, RTO is ring trip output, RTQ is response detection output, 30 is count output, CL
is a clock signal, and t ₁ to t ₁₁ and t ₁ ′ to t ₁₀ ′ are time points.

Claims (1)

[Claims] 1. In a ring signal sending circuit that performs a ring trip operation by detecting a direct current superimposed on a constant cycle ring signal current in response to a ring signal response, a comparison circuit that outputs one logical value during a period in which the ringing signal current is determined to be equal to or higher than the reference value, and outputs the other logical value during a period in which the ringing signal current is determined to be lower than or equal to the reference value; a first delay circuit that delays the output of the comparison circuit by a half period of the calling signal current; and a first gate circuit that outputs an AND of the output of the delay circuit and the output of the comparison circuit. , a second delay circuit that delays the output of the first gate circuit by a time corresponding to the pulse width of the pseudo pulse output by the first gate circuit before responding to the call signal; and a second gate circuit that outputs an AND of the output and the output of the second delay circuit, and the second gate circuit detects a direct current superimposed on the calling signal current. Features a ring trip method.