JPS6111017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication line continuity test method in a four-wire exchange.

In conventional space division switches, some kind of line continuity test is performed when the line is closed for each call.
However, in a 4-wire switch, such as a time-division switch, communication path conduction is generally required for each call, in order to improve the reliability of components and due to the inherent nature of the time-division switch, which uses circuits in time-division multiplexing. It was common practice to conduct no actual tests, and instead conduct pilot tests at regular intervals. However, in this pilot test, it is not always possible to test the multi-channel individual circuit portion of the communication path, so there is a risk that failures may occur and the quality of service may deteriorate.

The present invention has been developed by temporarily causing impedance mismatch in a two-wire four-wire switching circuit (generally a hybrid circuit), which is an essential device in a four-wire switching system that accommodates two-wire analog lines. It is an object of the present invention to provide a communication path continuity test method which solves the above-mentioned drawbacks by detecting reflected signals and conducting a continuity test of the communication path used in the call.

In order to achieve the above object, the present invention includes an impedance changing circuit for impedance mismatching on the 4-wire side output of a hybrid, and a detection circuit for the same output voltage.
The continuity test is performed by providing a control device that controls the impedance changing circuit and the output voltage detecting circuit.

Next, embodiments of the present invention will be described with reference to the drawings.

The figure is a block diagram showing one embodiment of the present invention. The subscriber SUB is generally two-wire and is accommodated in a four-wire exchange via a subscriber circuit LC on the exchange side. In this figure, for the sake of clarity, a time division switch is cited as a representative example of a four-wire switch, but the same applies to four-wire switches using electronic switches or mechanical connections. In this case, since the communication path section of the exchange is time-division multiplexed, all two-wire lines are
After being separated in one direction by a line conversion circuit (hybrid circuit HYB), it is converted into digital data by an analog-to-digital conversion circuit A/D or D/A. The digitally converted audio is sent to a multiplexer
It is multiplexed by MUX and connected to the time division communication path TDSW. Similarly, in the case of a two-wire analog transformer, it is connected to an exchange after two-wire/four-wire conversion.

In such a time-division exchange, in order to conduct a continuity test of a communication path like a space-division exchange for each call, a lead-in relay is installed in the subscriber circuit LC or trunk circuit TRK to ensure continuity at both ends. Whether or not it needs to be done through audio. This is because, as can be seen from the figure, in a time division switch, filters LPF and BPF are inserted in each connection circuit, and only voice signals can pass, not DC signals. Therefore, the subscriber circuit LC and the trunk circuit TRK circuit became complicated and uneconomical. However, with this system, a temporary impedance mismatch occurs in the two-wire/four-wire conversion circuit essential to this time-division switch, which causes reflections in the hybrid circuit HYB, which temporarily interrupts calls. Signals sent from within the route are re-introduced into the communication route. In particular, during exchange connection operations, when the called party is ringing, the called party's receiving exchange (or the corresponding exchange if it is within the own office)
Since the ringback tone is sent back to the caller, the exchange controller CONT controls the impedance change circuit IMP to temporarily transmit the ringback tone within the allowable range of service standards for the calling subscriber. hybrid
Change the impedance so that the balance of the HYB becomes mismatched, and check the presence or absence of reflected signals using the voltage (or current) detection circuit DET connected to the 4-wire side output of the hybrid HYB instead of conducting a continuity test. In this case, when the called subscriber answers, the communication circuit is closed at both the originating and receiving ends, and if there is still a mismatch at the originating hybrid HYB, oscillation will occur. Therefore,
Immediately after confirming the reflected output of the ring back, the impedance changing circuit IMP is restored to return to a normal impedance matching state. This control is performed by the output detection circuit DET or the control device CONT.

In this method, the reflected output detection circuit is connected directly to the 4-wire output side of the hybrid.
It can be easily assumed that the ringback tone receivers are arranged centrally throughout the communication path.

As explained above, the present invention temporarily mismatches the impedance of the two-wire/four-wire conversion circuit to which the calling party is connected while the calling party is returning a ringback tone. By causing a reflection and measuring the reflected output, the conduction state of the communication path can be confirmed.

[Brief explanation of the drawing]

The figure shows, in partial block diagram form, one embodiment of the invention. SUB...Subscriber, LC...Subscriber circuit, HYB...
…2-wire 4-wire conversion circuit (hybrid circuit), IMP
...Hybrid impedance change circuit, BPF
... Band pass filter, LPF ... Low pass filter, A/D, D/A ... Analog-to-digital conversion circuit, MUX ... Multiplexing circuit, TDSW ... Time division multiplexing channel, TRK ... Trunk circuit,
CONT...Control circuit.

Claims (1)

[Claims] 1. A 4-wire switch that has a network configuration in which the up and down lines are separated and integrated, and in a switch that accommodates 2-wire analog lines, the 4-wire output side of the 2-wire 4-wire conversion circuit and the analog/digital An impedance change circuit of the 2-wire 4-wire conversion circuit is provided between the conversion circuit, an output voltage (or current) detection circuit is connected to the output side of the 4-wire side, and the impedance change circuit and voltage (or current) detection circuit are connected to the output side of the 4-wire side. A communication line continuity test method for a four-wire exchange, which is equipped with a control device that controls the circuit, and performs a continuity test including an analog-to-digital conversion circuit for each call using a ring back tone.