JP2967614B2 - Terminal connection detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal connection detection system, and more particularly, to a terminal connection detection system using an AMI signal.

[0002]

2. Description of the Related Art Generally, in a digital line circuit accommodated in a private branch exchange, even if a line is not connected to a terminal, the terminal is connected due to crosstalk from a line to which another terminal is connected on a transmission line. May be erroneously identified as if they were being executed, and erroneous processing may occur. For this reason, a method of detecting the presence / absence of connection of a terminal that is not affected by crosstalk is required.

Conventional terminal connection detection is based on a method of determining that a terminal is connected when a DC current, which is a supply current to a terminal flowing through a transmission line, exceeds a certain threshold value, a method of determining that a terminal is connected, and a method of determining data uniquely determined for each line. The digital line circuit sends the data on the control channel (D channel) to the terminal side, and the terminal side returns the same data on the control channel so that the data transmitted on the digital line circuit side and the received data on the terminal side are transmitted. There has been a method of detecting terminal connection by comparing.

[0004]

Among the conventional terminal connection detection methods, the current detection method requires the addition of a circuit to the transmission line for current detection, and this additional circuit deteriorates the balance of the transmission line. And the noise resistance may be degraded. Further, the power that can be supplied by the terminal decreases due to the voltage drop by the current detection circuit. Further, depending on the terminal, there may be a configuration that does not require the supply of current from the transmission line. In this case, however, it is necessary to add an unnecessary current consuming circuit to the main body to indicate the connection of the terminal.

In addition, the method of sending back the only data determined on the control channel for each line has a problem that the load of the protocol between the digital circuit and the terminal increases, resulting in a reduction in processing capacity and an increase in cost. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a terminal connection detection system which can detect a terminal connection without adding an extra circuit to a transmission line or increasing protocol restrictions. .

[0007]

SUMMARY OF THE INVENTION A terminal connection detection system of the present invention is a private branch exchange accommodating a terminal via a digital line circuit using a two-wire time-division transmission line system based on an AMI signal accommodated in a private branch exchange. In the terminal connection detection method, a central processing unit that mediates various controls between the private branch exchange main body and the terminal, a unit that holds a bit pattern determined by the central processing unit, and an AMI signal that is transmitted according to the bit pattern. Means for controlling the polarity of the first bit “1” for each burst, means for identifying the polarity of the first bit “1” of one burst of the AMI signal received from the terminal, and the received AMI signal Means for comparing the polarity of "1" of the first bit of one burst of the AMI signal with the polarity of "1" of the first bit of the transmitted AMI signal. A line circuit, and means for identifying the polarity of "1" of the first bit of one burst of the AMI signal received from the digital line circuit, the A received
The first bit "1" of one burst of the AMI signal has the same polarity as the polarity of "1" of the first bit of one burst of the MI signal.
And a terminal that transmits the information.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention.
The digital line circuit 1 includes a central processing unit 1, a polarity control order holding circuit 9 that holds a bit pattern determined by the central processing unit 7, and a first bit “AMI” for each burst of an AMI signal transmitted according to the bit pattern. A polarity control circuit 8 for controlling the polarity of "1", a data identification circuit 6 for identifying the polarity of "1" of the first bit of one burst of the received AMI signal, and a first bit of one burst of the received AMI signal A polarity comparison circuit 10 is provided for comparing the polarity of “1” with the polarity of the first bit “1” of the transmitted AMI signal. Also, the terminal 2 transmits a data identification circuit 14 for identifying the polarity of “1” of one burst of the received AMI signal, and transmits the received AMI signal with the same polarity as the polarity of “1” of the first bit of one burst of the AMI signal. First of AMI signal of transmission signal
A polarity control circuit 15 for controlling the bit “1” is provided.

The digital line circuit 1 and the terminal 2 are connected to an AMI
Signals are transmitted and received by a two-wire time-division bidirectional transmission method using codes. The signal AMI-encoded by the AMI encoding circuit 3 of the digital line circuit 1 is output to the transmission path by the line drive circuit 4 of the digital line circuit 1. The AMI signal received from the terminal 2 to the automatic equalization amplifier 5 of the digital line circuit 1 is identified by the data identification circuit 6. This data identification circuit 6
It has a function of identifying not only the I signal “1.0” but also the polarity of the AMI signal “1”.

Central processing unit 7 of digital line circuit 1
Writes a unique bit pattern for each circuit into the polarity control order holding circuit 9 of the digital circuit 1. The polarity control order holding circuit 9 uses the written bit pattern to
The AMI encoding circuit 3 is controlled via the polarity control circuit 8 so that the polarity of “1” of the first bit (hereinafter referred to as a leading flag) of the transmission signal of the AMI signal is set to “+” for each burst or “ − ”. (Because the AMI signal is transmitted / received, the first bit is always “1”.) For example, the polarity of the reading flag “1” is set to “+, −,
"+, +", "+,-, +, +" ...
-, +, + "Is repeated. Where "+,-,
It is assumed that there is no other circuit that sends out “+, +”.

The polarity comparison circuit 10 compares the polarity of the reading flag identified by the data identification circuit 6 with the bit pattern written in the polarity control order holding circuit 9, and when all the bit patterns match, If the information indicating that the bit matches the central processing unit 7 or if there is any mismatch bit in any one of the bit patterns,
Information indicating the mismatch is transmitted to the central processing unit 7. In this example, if the polarity of "1" of the leading club of the received signal is "+,-, +, +", information indicating that they match is transmitted to the central processing unit 7.

On the other hand, the terminal 2 has an AMI encoding circuit 11,
It has a line drive circuit 12, an automatic equalizing amplifier 13, a data discriminating circuit 14, and a polarity control circuit 15, and as shown in FIG. 2, the reading flag "1" of the received signal discriminated by the data discriminating circuit 14 of the terminal 2. With the same polarity as the polarity,
It sends the leading flag of the transmission signal of terminal 2. When the reading flag of “+1” is transmitted as shown in FIG. 2A, the reading flag of “+1” is also returned from the terminal side, and as shown in FIG. 2B, the reading of “−1” is performed. If the flag is sent, the terminal
A reading flag of "1" is returned. With this function, the digital line circuit 1 can identify whether the received signal is a signal transmitted by a terminal or a signal received by crosstalk on a transmission path.

[0013]

As described above, according to the present invention, the connection of the terminal is detected by using the polarity of the leading flag of the AMI signal. Can be detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIGS. 2A and 2B are diagrams illustrating examples of the polarity of an AMI signal on a transmission line, where FIG. 2A illustrates a case where a reading flag of “+1” is transmitted, and FIG. 2B illustrates a case where a reading flag of “−1” is transmitted; It is a figure showing a case.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Digital line circuit 2 Terminal 3 AMI coding circuit of digital line circuit 4 Line drive circuit of digital line circuit 5 Automatic equalizing amplifier of digital line circuit 6 Data identification circuit of digital line circuit 7 Central processing unit of digital line circuit 8 Digital Polarity control circuit of line circuit 9 Polarity control order holding circuit of digital line circuit 10 Polarity comparison circuit of digital line circuit 11 AMI coding circuit of terminal 12 Line drive circuit of terminal 13 Automatic equalizing amplifier of terminal 14 Data identification of terminal Circuit 15 Terminal polarity control circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04M 3/00 H04M 3/26 H04L 25/49 H04Q 3/42 104-105 H04Q 3/545 H04Q 3/58 101-107

Claims (1)

(57) [Claims] 1. A terminal connection detection method for a private branch exchange accommodating a terminal via a digital line circuit using a two-wire time-division transmission line system based on an AMI signal accommodated in a private branch exchange. A central processing unit that mediates various controls between the central processing unit, a unit that holds a bit pattern determined by the central processing unit, and a polarity of a first bit “1” of an AMI signal transmitted according to the bit pattern for each burst. Control means; means for identifying the polarity of "1" of the first bit of one burst of the AMI signal received from the terminal;
Means for comparing the polarity of the "1" of the first bit of one burst of the I signal with the polarity of the "1" of the first bit of the transmitted AMI signal; and a signal received from the digital line circuit. Means for identifying the polarity of "1" of the first bit of one burst of the AMI signal, and the first bit of the AMI signal having the same polarity as the polarity of "1" of the first bit of one burst of the received AMI signal. A terminal transmitting means for transmitting 1-bit “1”.