JPH02288589A - 2-wire/4-wire conversion circuit - Google Patents

Abstract

PURPOSE:To reduce the deterioration in the echo loss characteristic by turning on a switch circuit when a feeding circuit reaches the electronic letter coil mode from the constant current mode so as to connect a coil in parallel with a termination resistor. CONSTITUTION:When a load 20 of an opposite exchange 19 is large and a feeding circuit 10 is at the outside of a constant current region, the phase of an AC signal is deviated due to the effect of an inductance of the electronic letter coil in the feeding circuit 10. Then a detection circuit 11 detects the current and a switch circuit 18 in a balancing network 13' is closed by the detection current and a coil 17 equivalent to the inductance of the electronic letter coil is connected in parallel with a termination resistor 16 to correct the phase. Thus, the impedance is matched between a 2-wire talking line 8' and the balancing network 13'. Thus, the deterioration in the echo loss characteristic is reduced.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a 2-wire/4-wire conversion circuit used in a signal conversion circuit that converts a 2-wire signaling system signal in a telephone exchange into a PCM line digital signal. The present invention relates to circuits, and in particular to the configuration of a power feeding mode adaptive balancing network.

[Conventional technology]

Conventionally, in the type of 2-wire/4-wire conversion circuit, as shown in Fig. 2, the power supply circuit 10 connected to the 2-wire communication path 8 side deviates from the constant current state and enters the electronic letter coil state. At that time, the balancing network 13 did not have a circuit for reducing the deterioration of the reverberation loss characteristics due to the coil component.

[The problem that the invention attempts to solve]

In the conventional balancing network 13 described above, 2
In the power feeding circuit 10 connected to the line communication path 8, when the power feeding mode is switched from the constant current mode to the electronic letter coil mode, the inductance of the nine electronic letter coils connected to the 2υ terminal causes the two-wire communication path 8flll and There was a problem in that the impedance balance with the balancing network 13 side was disrupted and the reverberation loss characteristics deteriorated.

[Means to solve the problem]

The 2-wire/4-wire conversion circuit according to the present invention was made in order to improve the above-mentioned conventional problems, and includes a current detection circuit in the power supply circuit and an electronic letter coil in the power supply circuit in the balancing network. It has an equivalent coil and a switch circuit for switching its connection.

[For production]

In the present invention, when the power supply circuit leaves constant current mode and enters electronic letter boil mode, the switch circuit is turned on and P! A coil is connected in parallel to the fi6 resistor to correct the phase.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

No. 1 C is a circuit diagram of an embodiment of the 2-wire/4-wire conversion circuit according to the present invention. In the same figure, a hybrid transformer 1 has a load 20 of a counterpart exchange 19 and an input/output terminal 21.
．． a coil 2 on the two-wire communication path side connected via 22;
It is configured to include a coil 3 on the balancing network side, a coil 4 on the 4-wire receiving side, and a coil 5 on the 4-wire transmitting side.

In addition, 6, T is earth energy. In addition, input/output terminal 21.2
A power supply 9, a power supply circuit 10, and a power supply current detection circuit 11 are connected to the two-wire communication path 8' connected to the power supply 2. Note that 12 is earth energy. Furthermore, the balance network 13' includes a capacitor 15 with the same capacity as the DC cut capacitor 14, a terminating resistor 16, a coil 1T equivalent to the electronic letter coil in the power supply circuit 10, and a switch circuit 18 for switching the connection. and is marked S#.

This 2-wire/4-wire conversion circuit configured as shown in FIG. The phase of the AC signal shifts due to the influence of the inductance.

Therefore, current detection is performed by the detection circuit 11, and this detected current closes the switch circuit 18 in the balancing network 13', and a coil 17 equivalent to the inductance of the electronic letter coil is connected in parallel with the terminating resistor 16. The phase will be corrected. Therefore, the impedance is matched between the two-wire communication path 8' and the balance sync network 13'.

〔Effect of the invention〕

As explained above, according to the present invention, the power supply circuit connected to the two-wire communication path exits the constant current mode and sends an electronic letter;
When the coil mode is set, a coil with the same inductance as the electronic letter coil is automatically connected to the balance sync network, and the phase is corrected and impedance is matched, which is extremely effective in reducing the deterioration of the echo loss characteristics. You can get the same effect.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a 2-wire/4-wire conversion circuit based on a water valve, and FIG. 2 is a circuit diagram showing a conventional 2-wire/4-wire conversion circuit. 1φeφt hybrid transformer, 2, 3, 4゜5...
・War coil, 6.7-φ... ground%, 8'... 2-wire communication path, 9... power supply, 10... power supply circuit, 11Φ... detection circuit, 12... - Earth air, 13' φφ cost and balance sink network, 14, 15--φ DC cut code/de/su, 16・e-・terminal resistor, 1T-Kenichi-
Coil equivalent to electronic letter coil, 19... mating exchange, 20... load, 21.22-@-φ input/output terminal. 71 ward map 2

Claims (1)

[Claims] A current detection circuit is provided in a two-wire communication path that is connected to a load of the opposite exchange and has a power supply circuit, and a coil equivalent to the electronic letter coil in the power supply circuit and the output current of the detection circuit are provided in the balancing network. A 2-wire/4-wire conversion circuit comprising a switch circuit for connecting and controlling the coil.