JPH0321131A - Private branch extension system - Google Patents

Abstract

PURPOSE:To adopt a poling selecting system as a host computer transmission control system by providing respective MODEM devices on the host computer side and terminal side with pseudo carrier generation detecting circuits. CONSTITUTION:When a data sending requesting signal is outputted from a data terminal equipment 8 to the host computer 1, the signal is inputted to a MODEM device 4 through a time division multiplexing device 7, a high speed digital line 6 and a time division multiplexing device 5. The input signal is converted into pseudo carrier information by the pseudo carrier generation detecting circuit 4a in the device 4 and the converted information is transmitted to the pseudo carrier generation detecting circuit 2a in the MODEM device 2. The circuit 2a reconverts the received pseudo carrier information into a data transmission requesting signal and outputs the converted signal to the host computer 1. Thereby, the computer 1 can receive the data transmission requesting signal independently of a normally-ON carrier detecting signal outputted from the device 2a.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention relates to a data transmission system that connects a host 1 to a computer and a data terminal device using a time division multiplexer and a high-speed digital line. and a time division multiplexing device.

[Prior Art] Conventionally, in a data transmission system that connects a computer and a data terminal device (hereinafter referred to as a terminal device) to a host 1 using a time division multiplexing device and a high-speed digital line, a computer and a data terminal device (hereinafter referred to as the terminal device) are connected to a host 1. When extending the distance between the time division multiplexing device and the time division multiplexing device within the premises, an extension device, such as a modem device or an optical modem device, is placed facing between the host I computer and the time division multiplexing device. Extending the distance between modem devices. At this time, data transmission between modem devices is performed under predetermined interface conditions (CCI
This is done in TT Recommendations V24-, V35, etc.

In such a case, when the time division multiplexing device and the host computer perform data transmission via a modem device, the modem device and the host computer use the clock of the high-speed digital line to which the time division multiplexing device is connected as the master clock. Therefore, it is essential to operate in system synchronization in accordance with this master clock.

For this reason, it is necessary to always keep the carrier signal on between the modem devices disposed opposite each other, and keep the carrier detection signal output from the modem device to the host computer in the on state.

[Problems to be Solved by the Invention] However, the above-described conventional premise extension system has the drawback that the polling selection system cannot be adopted as a transmission control system for the host computer.

In other words, in the polling selection method,
The host computer inquires of the terminal device as to whether there is a data transmission request, and if there is a data transmission request from the terminal device, it receives data from the terminal side. Therefore, Phos}
~The computer must monitor data transmission requests from terminal devices. Typically, when a modem device located on the terminal device side detects a data transmission request signal from the terminal device, it transmits a carrier signal to a modem device located on the host computer side. The modem device on the host computer side that receives this carrier signal outputs a carrier detection signal to the host computer. Therefore, host compico. At first, it is sufficient to recognize this carrier detection signal as a data transmission request signal from the terminal device.

However, as mentioned above, in the conventional premise extension system, the modem devices on the terminal side and the host computer side constantly transmit carrier signals, so the carrier detection signal output from the modem device on the host computer side to the host computer is It is always on. therefore,
Since the carrier detection signal cannot be recognized as a data transmission request signal from the terminal device, it has been impossible to employ the polling selection method in the past.

[Means for Solving the Problems 1] The premises extension method of the present invention is such that when a modem device connected to a time division multiplexing device receives a data transmission request signal transmitted from a data terminal device, A means is provided to forcibly assign a polarity change point to the sent data and transmit the data, and the modem device connected to the host computer transmits the data to the host computer when the received data has a polarity change point. Means for outputting a request signal is provided.

[Operation] When the modem device connected to the time division multiplexing device receives a data transmission request signal from the data terminal device, it forcibly scrambles the data received after the data transmission request signal. Give the polarity change point and transmit. On the other hand, when a modem device connected to a host computer receives data having a polarity change point,
Outputs a data transmission request signal to the host computer. This allows the host computer to recognize the data transmission request signal regardless of the always-on carrier detection signal output from the modem device.

[Example code] Next, the present invention will be explained with reference to the drawings.

Figure ↑ is a block diagram of a data transmission system in one embodiment of the premises extension system of the present invention.

Above are hosts 1 to computers, 2 is a modem device on the host computer side, 3 is a local cable, 4 is a modem device on the terminal side, 5 is a time division multiplexer on the host computer side,
6 is a high-speed digital line, 7 is a time division multiplexing device on the terminal side, and 8 is a terminal device. The modem device 2.4 includes pseudo carrier generation detection circuits 2a and 4a, which will be described later.

The clock of the high-speed digital line 6 connecting the time division multiplexers 5 and 7 is used as the master clock, and the modem devices 2 and 4 and the host computer 1 operate as slaves. The modem device 2 is set so that a carrier signal is always sent. Therefore, the carrier detection signal output from the modem device 2 to the host computer 1 is always on.

Next, an outline of the operation when the terminal device 8 sends the data sending request signal RS to the host computer 1 in this state will be explained.

Data transmission request signal R sent from data terminal device 8
S is a terminal side time division multiplexing device 7, a high-speed digital line 6
, and the terminal side modem device 4 via the host computer side time division multiplexing device 5. Then, it is converted into pseudo carrier information in the pseudo carrier generation detection circuit 4a of the terminal side modem device 4, and this pseudo carrier information is transmitted to the pseudo carrier generation detection circuit 2a of the host computer measurement modem device 2. The pseudo carrier generation detection circuit 2a reconverts the received pseudo carrier information into a data transmission request signal and outputs it to the host computer 1-. As a result, the boss l-computer 1- can receive the data transmission request signal RS.

Next, the above-mentioned pseudo carrier generation detection circuits 2a and 4a will be explained in detail.

FIG. 2 is a block diagram of the modem devices 2 and 4 without showing details. The modem W4 has a pseudo carrier generation detection circuit 4a and a transmitter 4b that modulates data input from the terminal side, and the pseudo carrier generation detection circuit 4a has a pseudo carrier generation detection circuit 4a that modulates data input from the terminal side.
It has a scrambler 4c that scrambles and outputs the data input from b.

On the other hand, the modem device M2 has a pseudo carrier generation detection circuit 2a.
and a receiver 2b that demodulates the data. This pseudo carrier generation detection time i\fi2a is the scrambler 4
It has a descrambler 2c that restores the scrambled data in step c, and an identification circuit 2d that identifies whether there is a polarity change point in the data sent from the scrambler 4C and outputs an identification signal. .

Next, the operation will be explained. As described above, the data transmission request signal RS is sent from the terminal device 8 to the transmitter 4b before data is sent. That is, this data transmission request signal RS turns on when the data output from the transmitter 4b to the scrambler 4c is significant, and turns off when it is not significant.

When the data transmission request signal RS is on, the scrambler 4b scrambles the data input from the transmitter 4b, thereby forcing the data to have a polarity change point and outputting the data. Further, when the data transmission request signal RS is off, the scrambler 4c maintains the output at a predetermined level, for example, in the status state of "o" or "1". That is, in this scrambler 4c, the ON and OFF states of the data transmission request signal RS are converted into the presence or absence of a polarity change point of the data output from the scrambler 4c. In other words, the data transmission request signal R. S is converted into information indicated by the presence or absence of a polarity change point in the data.

On the other hand, the test scrambler 2c performs test scramble on the data input from the scrambler 4c and outputs the data to the receiver 2b. An identification circuit 2d, which will be described later, turns on an identification signal and outputs it to the receiver 2b when there is a polarity change point in the data sent from the scrambler 4c, and turns off the identification signal and outputs it to the receiver 2b when there is no polarity change point. Output. Therefore, when the polarity change point I is sent from the modem device 4 to the modem device W2, the identification signal is turned on and off in the identification circuit 2d.
After the data transmission request signal RS is turned on and off again, it is sent to the host 1 to the computer via the receiver 2b.

Next, the identification circuit 2d will be explained.

FIG. 3 is a block diagram of the identification circuit 2d. 2↓ is an n-bit counter, which receives a data clock CLK synchronized with data from the input terminal A and performs operations starting from the counter 1. This data clock CLK is extracted from the data signal by a clock extraction means (not shown). This counter 21 is cleared and outputs "0" from the output terminal B when the data input to the clear terminal C9 10 L is "1". on the other hand,
When the data input to the clear terminal CL is "O", when the count is started and n bits have been counted, the output terminal B
``1'' is output. Note that n is determined according to the configuration of the scrambler 4c and descrambler 2C described above. 22 is a trigger type flip-flop, and when the signal input to the set terminal S is turned on, the output terminal Q is set to "1", and the reset terminal R is set to "1".
When the input signal is turned on, the output terminal Q is reset to "O".

Next, the operation will be explained. When the data input to the input terminal (3) of the identification circuit 2d becomes "1", the flip-flop 22 is set and the output terminal Q becomes rlJ, indicating that a polarity change point exists. On the other hand, when n bits of data input to the manual terminal ■ become "0" consecutively, "1" is sent from the output terminal B of the counter 21 to the flip-flop 22.
is output, the flip-flop [7p22ζ] is reset, and the output terminal Q becomes "0", indicating that there is no polarity change point. In other words, the input terminal ■ of the identification circuit 2d
During the period when there is a polarity change point in the data input to the input signal, the output terminal Ji of the identification circuit 2d becomes 1-1.
The output terminal J of d becomes "0". As a result, the data transmission request signal RS is reconverted and output to the receiver 2b.

Note that in the system ellipse of FIG. 1 described above, the host computer 1 and the terminal device 8 are connected to the
However, as shown in FIG.
It goes without saying that the same operation as in the embodiment shown in the upper figure can be performed even in the case where the multi-boin 9 is connected to the multi-boin 1 by the branch dedicated line 10.

Furthermore, although a scrambler is used as a method for forcibly providing polarity change points to data, the present invention is not limited to this method, and it goes without saying that other methods may be used to provide polarity change points.

[Effects of the Invention] As explained below, according to the premises extension system of the present invention, when the modem device connected to the time division multiplexing device receives a data transmission request signal from the data terminal device, it sends the data transmission request signal. Forcibly change the polarity change point by scrambling the data received after the signal.
j, send it again.

On the other hand, a modem device connected to a host computer
When data having a polarity change point is received, a data transmission request signal is output to the host computer. This allows the host computer to recognize the data transmission request signal regardless of the always-on carrier detection signal output from the modem device. Therefore, when the host computer inquires of the terminal device whether or not to send data, the terminal device can send a data transmission request signal to the host 1 to the computer, so the polling selection method is adopted as the transmission control method for the host computer. can do.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a data transmission system using a point-to-point connection in an embodiment of the present invention, FIG. 2 is a block diagram of a pseudo carrier generation detection circuit of the same data transmission system, and FIG. 3 is a block diagram of a pseudo carrier generation detection circuit of the same data transmission system. FIG. 4 is a block diagram of the identification circuit of the occurrence detection circuit, and FIG. 4 is a block diagram of a data transmission system using a multi-boin 1 connection according to another embodiment. 2, 4...Modem device, 2a, 4a...Pseudo carrier generation detection circuit, 2C...Descrambler, 2d...
・Identification circuit, 4C...scrambler

Claims (1)

[Claims] A time division multiplexing device is disposed facing each other between a host computer and a data terminal device, and the time division multiplexing device is connected by a high-speed digital line. In the premises extension method, in which the distance between the host computer and the time division multiplexing equipment is extended by placing modem equipment facing each other between the data terminal equipment and the modem equipment connected to the time division multiplexing equipment, A modem device connected to a host computer is provided with means for forcibly giving a polarity change point to the data sent from the data terminal device and transmitting the data when a transmitted data transmission request signal is received. 1. A premises extension system characterized by comprising means for outputting a data transmission request signal to a host computer when there is a polarity change point in the data transmitted.