JPH07273750A - Interface circuit for code conversion - Google Patents

Abstract

PURPOSE:To eliminate classifications of reception parts to gain a standardization effect in the stage of production and to prevent the occurrence or erroneous work at the time of device installation or the like. CONSTITUTION:The device consists of a transmission part 1, which takes the primary group signal from a PCM multiplexing part as the input and converts the code from the unipolar code to CMI, and a reception part 2 which takes the primary group signal from a transmission line as the input and decodes the code from CMI to a unipolar code. A frequency discriminating circuit 16 of the transmission part 1 discriminates it from the clock signal whether the frequency of the transmission line is in 1.5M band or 2.0M band and outputs the discrimination result as a frequency signal. This frequency signal is sent to a phantom circuit of the transmission line 3 through a frequency signal superposing circuit 15. In the reception part 2, the frequency signal from the phantom circuit is received by a frequency signal reception circuit 25 and is inputted to a PLL circuit 26 to switch the oscillation frequency of the VCO.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a code conversion interface.
More particularly, the present invention relates to an interface circuit for converting a code of a digital signal on the device side into a code on the transmission line side or for decoding in a transmission line side interface of a digital multiplex terminal device.

[0002]

2. Description of the Related Art Conventionally, this kind of code conversion interface has been used.
The transmission circuit is divided into a transmission unit and a reception unit. The transmission unit is provided on the transmission device side and converts a transmission digital signal into a designated transmission path code. On the other hand, the receiving unit is provided on the receiving device side and decodes the received digital signal from the transmission line into an in-device code. Normally, the intra-device code is a unipolar, and the transmission line code is a bipolar or CMI (coded mar) for removing a DC component or for reproducing a timing pulse.
k inversion) or the like is used.

Further, the mounting structure of the transmitting unit and the receiving unit is a small module structure in which all the components are mounted on a small board. This is treated as one unit component and mounted in a predetermined package on the device side for use.

FIG. 2 shows a block diagram of an interface circuit of this type used in a PCM terminal device as an example.

In the transmitter 4, the digital signal (primary group signal) from the PCM terminal station multiplexer is first unipolar / C.
With the MI converter 41, NRZ (Non return) on the device side
from the unipolar code to the CM on the transmission line side
The signal is converted into the I code, then powered up by the driver circuit 42, circuitally insulated by the relay transformer 43, and sent to the transmission line 6.

In the receiving section 5, the digital signal (primary group signal) from the transmission line 6 first passes through the relay transformer 51 and is input to the equalizer circuit 52 to be waveform-shaped.
Next, after being amplified by the amplifier 53, the CMI / unipolar converter 54 decodes the CMI code on the transmission path side into the NRZ unipolar code on the device side, and sends it to the PCM terminal station separating section. The timing signal required when the received digital signal is decoded by the CMI / unipolar converter 54 is the PLL.
It is supplied from the circuit 55. The PLL circuit 55 generates and outputs the timing signal by the VCO using the received digital signal as a synchronizing signal.

Although there is no classification according to the frequency of the digital signal in the transmitter 4, if the frequency of the digital signal in the receiver 5 is different, the natural oscillation frequency of the VCO of the PLL circuit 55 is correspondingly different. , Switching by this frequency is required. In the case of the primary group of PCM terminal equipment, the frequency of this digital signal is 1.5 MHz.
Since there are two types, z band and 2.0 MHz band, the receiving unit 5
There are also two types, and either one is selected and used.

[0008]

As described above, in the conventional code conversion interface circuit, it is necessary to prepare a plurality of receiving units for each frequency of the transmission path digital signal. For example, in the case of the PCM primary group, Transmission line frequency is 1.5 MH
Two types are required, one for the z band and one for the 2.0 MHz band. In many cases, which of these is to be used is decided at the time of installation of the device, etc. Normally, due to the installation work procedure, a person instructs the receiving side from the transmitting side at that time. The receiving side selects and responds to the corresponding receiving unit according to this instruction.

Providing a plurality of types of receivers in this way increases the manufacturing cost and management man-hours at the manufacturing stage, and also causes erroneous work due to human instructions from the transmitter during installation. There is a problem that it is easy to do.

[0010]

A code conversion interface circuit according to the present invention comprises a transmitter for converting a digital signal from the device side into a code on the transmission line side and sending the code to the transmission line, and a digital signal from the transmission line. In a code conversion interface circuit consisting of a receiving section for decoding to the apparatus side and sending it to the apparatus side, a relay line with a neutral point tap on the transmission path side of each of the transmitting section and the receiving section. Means for forming an earth return phantom line in the transmission line, means for generating a frequency signal representing the frequency of the digital signal in the transmitting section and transmitting the frequency signal to the phantom line, and the frequency signal for the receiving section. And means for switching the internal operating frequency according to the reception.

The frequency signal may be generated by identifying the frequency of the digital signal and automatically generating from the identification result.

[0012]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of this embodiment.

In the transmitter 1, the digital signal (primary group signal) from the PCM terminal station multiplexer is first of all unipolar / C.
The MI converter 11 converts the NRZ unipolar code on the device side into the CMI code on the transmission path side, and then the driver circuit 1
It is powered up by 2, is insulated in the circuit by the relay transformer 13, and is sent to the transmission line 3.

In the receiving section 2, the digital signal (primary group signal) from the transmission line 3 first passes through the relay transformer 21 and is input to the equalizer circuit 22 to be waveform-shaped.
Then, after being amplified by the amplifier 53, the CMI code is decoded by the next CMI / unipolar converter 24 into the NRZ unipolar code on the device side, and is sent to the PCM terminal station separating unit. CM
A timing signal required for decoding the received digital signal by the I / unipolar converter 24 is supplied from the PLL circuit 25. The PLL circuit 25 generates and outputs the timing signal by the VCO using the received digital signal as a synchronizing signal.

The relay transformer 13 of the transmitter 1 and the relay transformer 21 of the receiver 2 each have a neutral point tap at the center of the winding on the transmission line side. By using this neutral point tap, the earth return type telecommunications line is superimposed on the transmission line 3.

The frequency discriminating circuit 14 of the transmitting section 1 inputs the clock signal of the device side, measures this frequency by an internal timer and counter, and the frequency of the transmitting signal is 1.5M.
Identify the band or 2.0M band. The identification result is input to the frequency signal superimposing circuit 15 as a frequency signal, and the logical level is 1 in the frequency band of 1.5 M and the logical level 0 in the frequency band of 2.0 M.
Is sent to the duplex line of the relay transformer 13.

The frequency signal receiving circuit 25 of the receiving section 2 receives the frequency signal from the duplex line and inputs it to the PLL circuit 26. This causes the PLL circuit 26 to switch the natural oscillation frequency of the VCO to the corresponding frequency.

In the transmitter 1, the frequency identification circuit 14 identifies the frequency from the clock signal and automatically generates the frequency signal. If the frequency is known in advance,
Alternatively, the frequency identification circuit 14 may be omitted by directly inputting the frequency signal to the frequency signal superimposing circuit 15 by manually operating the switch.

The signal code on the transmission path side is CMI, but bipolar or other codes can also be applied.

[0020]

As described above, in the code conversion interface circuit of the present invention, in the receiving section, the receiving frequency is automatically switched by the frequency signal transmitted from the transmitting section using the duplex line. Therefore, there is no need to prepare multiple reception units for each reception frequency, and only one type is required.

Therefore, due to the standardization effect, the manufacturing cost and management man-hours of the receiving unit are reduced, and at the time of installation, it is not necessary for the transmitting side to the receiving side to instruct the receiving side from the receiving side by the person, so that erroneous work can be performed. It has the effect of not occurring.

[Brief description of drawings]

FIG. 1 is a block diagram of this embodiment.

FIG. 2 is a block diagram of a conventional example.

[Explanation of symbols]

 1 Transmitter 11 Unipolar / CMI Converter 12 Driver Circuit 13 Relay Transformer 14 Frequency Identification Circuit 15 Frequency Signal Superimposing Circuit 2 Receiver 21 Relay Transformer 22 Equalizer Circuit 23 Amplifier 24 CMI / Unipolar Converter 25 Frequency Signal Receiver Circuit 26 PLL Circuit 3 Transmission line

Claims (2)

[Claims] 1. A transmission unit for converting a digital signal from the device side into a code on the transmission line side and sending out to the transmission line, and a receiving unit for decoding the digital signal from the transmission line into a code on the device side and sending out to the device side. In the interface circuit for code conversion consisting of, means for forming a relay line with a neutral point tap on the transmission line side of each of the transmission unit and the reception unit to configure a ground return duplex line on the transmission line. , A means for generating a frequency signal representing the frequency of the digital signal in the transmitting section and transmitting the frequency signal to the duplex line, and a means for receiving the frequency signal in the receiving section and switching the internal operating frequency thereby. Characterizing interface circuit for code conversion. 2. The code conversion interface circuit according to claim 1, wherein the frequency signal identifies the frequency of the digital signal and is automatically generated from the identification result.