JPH02177691A - Electronic letter coil - Google Patents

Abstract

PURPOSE:To realize the high vertical balance characteristics even with the signal states of various statuses by switching the inductance of a letter coil. CONSTITUTION:For the inductance L of an electronic letter coil, L=R2XR3XC is satisfied when the resistance values of registors 2 and 3 are set at R2 and R3 together with the capacity of the capacitor connected in parallel to the resistor 3 set at C respectively. If the capacities of capacitors 21-23 are set different from each other, the inductance T can be switched in 2<3>-1 (2<n>-1 in general) different ways as long as the ground potential or the potential of -5V is inputted to the input terminals 51-53 respectively. In this case, however, either one of capacitors 21-23 must always be connected to a circuit and therefore the voltage of -5V must be applied to either one of terminals 51-53. Thus it is possible to realize the high vertical balance characteristics even with the signal states of various statuses.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for converting one-line signaling signals in a telephone exchange into a PC.
This invention relates to an electronic letter coil used in a signal conversion circuit that converts M-line digital signals.

[Conventional technology]

FIG. 2 is a circuit diagram of an example of a conventional electronic letter coil.

The values of resistors 102 and 103 are respectively R1o2°R10
3. If the value of the capacitor 105 is C105, the inductance of the electronic letter coil is expressed by the formula (1), L = R1o2 was.

[Problem to be solved by the invention]

In the conventional electronic letter coil described above, when the impedance of the a and b wires becomes unbalanced due to the signal transmission state of the trunk of the telephone exchange or the signal conversion circuit, in order to improve the longitudinal balance characteristics, the a and b lines in the signal conversion circuit are To deal with this, it is necessary to change the impedance balance of the wire's electronic letter coil, but conventionally, the inductance of the electronic letter coil is fixed, so it is not possible to follow the optimal impedance balance state as the signal status changes. This is difficult, and even if it is a problem to specify the vertical balance only during a call, there is a drawback that the inductance of the electronic letter coil must be changed by changing the element constants for each opposing trunk.

[Means to solve the problem]

The electronic letter coil of the present invention includes a transistor constituting the letter coil, a plurality of capacitors that change the inductance of the letter coil, and a switching circuit that selectively connects the capacitor between the base of the transistor and ground. have.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a circuit diagram of an embodiment of the present invention.

In this embodiment, a negative power supply 5 is connected to the negative terminals of the primary coils of a plurality of relays 11 to 13, and the collectors of transistors 31 to 33 are connected to the positive terminals of the secondary coils, respectively. Ground G to which the emitters of the transistors 31 to 33 are connected, resistors 41 to 43 each connected to the emitters of the transistors 31 to 33, and input terminals connected to the other ends of the resistors 41 to 43, respectively. 51
~53, resistor 2 connected between the base and collector of transistor 1, resistor 3 connected between the emitter of transistor 1 and ground G, and connected between the base of transistor 1 and ground G. resistor 4 and switches 11' to 11', which become conductive when relays 11 to 13 are activated.
One end of the switch 13' is connected to one end of the capacitors 21 to 23, respectively, and the other ends of the switches 11' to 13' and the other ends of the capacitors 21 to 23 are connected in parallel to both ends of the resistor 4.

Here, when the potential of ground G is input to the input terminal 51, the transistor 31 is turned off, and the relay 11
does not operate, the switch 11' is opened, and the capacitor 21 is not connected to the circuit. Further, when a voltage of -5V is input to the input terminal 51, the transistor 31 becomes conductive (on) L, the relay 11 operates, the switch 11' closes, and the capacitor 2
1 is connected to the circuit. The same applies when the ground potential or the voltage of -5V is input to the input terminals 52 and 53. By the way, the inductance of the electronic letter coil is
When the resistance values of the resistors 2.3 are R2 and R3, respectively, and the capacitance of the capacitor connected in parallel with the resistor 3 is C, the formula <2) is obtained.

L = R2
By inputting the potential of ■, 2'-1 (- ultimately 2
It becomes possible to switch the inductance in the following manner. However, since one of the capacitors 21 to 23 must be connected to the circuit, the input terminal 5
A voltage of 15cm must be input to any one of 1 to 53.

〔Effect of the invention〕

As explained above, since the present invention can switch the inductance of the letter coil, in the signal conversion circuit of the PCM terminal equipment connected to the trunk of the exchange,
By adjusting the balance of inductance of the electronic letter coil used for signal transmission detection of the a and b lines, there is an effect that high longitudinal balance characteristics can be obtained even under various signal statuses.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional electronic letter coil. 1.31.32,33,101...transistor, 2
, 3, 4, 41, 42, 43, 102°103.104
...Resistor, 5...Negative power supply, 11°12.13.
...Relay, 21, 22.23 105...Capacitor, G...Ground.

Claims (1)

[Claims] An electronic device comprising a transistor constituting a letter coil, a plurality of capacitors that change the inductance of the letter coil, and a switching circuit that selectively connects the capacitor between the base of the transistor and ground. Letter coil.