JPH0121660B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an interface circuit in an exchange having a 2-wire to 4-wire conversion function.

An analog exchange that transmits and exchanges analog signals employs a 2-wire communication path. FIG. 1 shows such a conventional analog switching system 1, in which an analog communication path switch 11 is connected to a music-on-hold circuit 12, a paging circuit 13, and a plurality of circuits via two-wire communication paths. Set of extension subscriber line circuits 1
4 is connected. The music on-hold circuit 12 is an interface circuit for transmitting a hold tone to a telephone on hold connected to the extension subscriber line circuit 14, for example, the telephone 2A, via the analog call path switch 11. The input terminal is connected to a sound source 3 for hold music such as a music box or a cassette tape. Furthermore, the paging circuit 13 connects its output terminal to the loudspeaker 4.
When a specific number is dialed from any telephone, for example telephone 2B, the telephone 2B is connected to the paging circuit 13, thereby enabling the telephone 2B to perform loudspeaker broadcasting.

In such an exchange, the music on-hold circuit 12, paging circuit 13, and extension subscriber line circuit 14 connected to the analog communication path switch 11 are housed in separate printed circuit board units because their circuit functions are different. Ta. Even in 2-wire to 4-wire switching equipment such as PCM switching equipment, the manufacturing method of manufacturing these circuits individually and mounting them inside the housing has been inherited. However, this method requires a plurality of types of printed circuit board units for different functions for the interface circuit, which is not preferable from the point of view of cost and the efficiency of mounting the units within the housing.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an interface circuit that can convert a plurality of interface functions with one type of printed circuit board unit.

In the present invention, by providing the interface circuit with a function that enables signal transmission and reception between the conversion circuit and the outside without going through a 2-wire to 4-wire conversion means,
Achieve the above objectives.

The present invention will be explained in detail with reference to Examples below.

The same parts as in Fig. 1 are given the same reference numerals as in Fig. 2.
The figure shows a PCM switch that performs 2-wire to 4-wire switching. The PCM exchanger 5 includes a printed circuit board unit 51A having multiple interface functions.
51B,... are provided. These printed circuit board units each include an audio amplifier 511 for amplifying audio signals, a hybrid transformer 512 which is a conversion means used to convert a 4-wire circuit to a 2-wire circuit, and a hybrid transformer 512.
a balance circuit 513, a codec 514 for converting digital signals and analog signals, filter circuits 515, 516 for removing unnecessary frequency components from signals converted to analog signals and signals converted to digital signals, and A switching mechanism 517 is provided as switching means for converting functions.

Audio amplifier 5 of first printed circuit board unit 51A
11. Filter circuit 516 and codec 5
14 constitutes a music on-hold circuit by a switching mechanism 517. That is, the input terminals 518A and 518B (fourth terminal pair) of the audio amplifier 511 are connected to the sound source input terminals 31 and 32 to which the sound source 3 of the held music is connected, and one output terminal 517A of the audio amplifier 511 and the filter circuit. One input terminal 517B of the audio amplifier 516 is electrically connected to the strap wire 517C, and the other output terminal 517D of the audio amplifier 511 and the other input terminal 517E of the filter circuit 515 are electrically connected to each other by the strap wire 517F. The electrical signal supplied from the sound source is amplified and converted into a digital signal of a predetermined channel by the codec 514, and then sent to the output terminal 518C, which is the third terminal pair.
The signal is then sent to the channel switching device 53 via the PCM highway 52.

On the other hand, a hybrid transformer 512 and a balance circuit 51 arranged on the first printed circuit board unit 51A
3. Filter circuit 515 and codec 51
The other part of 4 constitutes a paging circuit by a switching mechanism 517. That is, since the terminals 517G and 517H connected to both ends of the characteristic impedance 512A of the hybrid transformer 512 are separated from the input terminals 517B and 517E of the filter circuit, the hybrid transformer 512 is a transformer exclusively used for outputting analog signals. The end on the two-wire side is connected to the terminal 518 which is the first terminal pair.
D, 518E to output terminal 4 connected to loudspeaker 4
1 and 42, when the digital signal is supplied to the codec 514 via the PCM highway 52 and the input terminal 518F, which is the second pair of terminals, the converted analog signal is output from the codec 514 and amplified by the loudspeaker 4. Broadcasting becomes possible.

The other printed circuit board units 51B, . . . constitute an interface circuit (extension subscriber line circuit) for the telephone set. That is, in the printed circuit board unit 51B, the input terminal 517B and the terminal 517
G is connected to the strap wire 517C, and input terminal 517E and terminal 517H are connected to the strap wire 517F.
are electrically connected to each other by terminal 5.
18D and 518E are connected to terminals 21A and 22A connected to telephone 2A, so telephone 2
The audio signal output from A is sent to the PCM hardware 52 from an output terminal 518C via a hybrid transformer 512, a filter circuit 516, and a codec 514. Further, the audio signal of another telephone transmitted from the PCM highway 52 to the input terminal 518F is supplied to the telephone 2A via the codec 514, the filter circuit 515 and the hybrid circuit 512.

The specific circuit operation in this PCM exchange will be explained using FIG. Assume that extension subscriber A and extension subscriber B are making an extension call using telephones 2A and 2B. In this state, extension subscriber A uses telephone 2.
When a hold button (not shown) of A is pressed, the central control device 55 detects this and sends channel change information to the channel change device 53. A digital signal of a hold tone is supplied to the channel switching device 53 from the sound source 3 connected to the input terminals 31 and 32 to a specific channel via the printed circuit board unit 51A. The channel switching device switches the digital signal supplied to the above-mentioned specific channel to the channel assigned to extension subscriber B's telephone 2B based on the channel switching information.
As a result, the hold tone is heard on the telephone 2B.

When extension subscriber A calls a third party who is away in this state, extension subscriber A presses the paging button if the telephone 2A in use is an electronic key telephone. As a result, central control device 55 identifies that telephone 2A has made a paging request, and sends channel switching information to channel switching device 53. As a result, the printed circuit board unit 5
The voice signal of extension subscriber A sent to PCM highway 52 via channel switching device 5
3 to the channel assigned to the paging circuit. Then, the digital signal is converted into an analog signal by the codec 514 in the printed circuit board unit 51A, and the output terminal 4
Subscriber A's voice is broadcast by loudspeaker 4 connected to terminals 1 and 42.

If the telephone 2A is a push button dial telephone or a rotary dial telephone, the extension subscriber A dials a predetermined number for paging. Outgoing register 56 receives the multifrequency signal or dial impulse, reads the dialed number, and sends it to central controller 55.
Transfer to. As a result, central control unit 55 identifies that telephone 2A has requested paging, and connects the telephone line of telephone 2A to the paging circuit in the same manner as described above.

In this way, according to this embodiment, one codec can be used independently for the transmitting circuit and the receiving circuit, so that the music on-hold circuit and the paging circuit can be integrated into the interface circuit board. This makes it possible to reduce the number of types of substrates.

As described in detail above, according to the present invention, it is possible to obtain an interface circuit that can convert a plurality of interface functions with one type of printed circuit board unit.

In this embodiment, a case has been described in which an extension is put on hold and the hold tone is sent to the extension via the music on-hold circuit, but the present invention is not limited to this, and the hold tone can be sent to the held outside line. Of course.

Further, in this embodiment, the sound source 3 and the loudspeaker 4 are used as examples of external circuits, but the present invention is not limited to this example.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional switch having a 2-wire to 4-wire conversion function, and Fig. 2 is a circuit diagram for explaining function conversion of an interface circuit by a switching mechanism of a printed circuit board unit in an embodiment of the present invention. 3 are circuit diagrams for explaining the operation of an exchange using a function-converted interface circuit. 5... PCM exchanger, 51... Printed circuit board unit, 517... Switching mechanism.

Claims (1)

[Claims] 1. A conversion means having a 2-wire to 4-wire conversion function, and a first converter connected to the 2-wire side end of the conversion means.
a second pair of terminals connected to one end of the four-wire side of the conversion means; and a third pair of terminals connected to the other end of the four-wire side of the conversion means. , a fourth terminal pair to which the third terminal pair is connected without going through the converting means; and a fourth terminal pair to which the third terminal pair is connected to the other end of the fourth wire side switching means for switching between connecting the third terminal pair to the fourth terminal pair;
When connected to the other end of the line side, a circuit that transmits a signal between the first terminal pair and the second and third terminal pairs by a 2-wire to 4-wire conversion function by the conversion means. while configuring, when the third terminal pair is connected to the fourth terminal pair by the switching means, a signal arriving from the fourth terminal pair is sent to the third terminal pair, An interface circuit comprising a circuit that transmits a signal arriving from the second pair of terminals to the first pair of terminals by passing the signal through the conversion means without using the 2-wire to 4-wire conversion function. . 2. The interface circuit according to claim 1, wherein the switching means selects whether to configure a paging circuit together with a music-on-hold circuit, a trunk circuit, or a line circuit. .