JPH04312044A - Modulator/demodulator device - Google Patents

Abstract

PURPOSE:To attain quick restoration without using another device even when a terminal continues to output a request to send by turning off a send request signal when the send request signal is active beyond a period determined in a system. CONSTITUTION:The send request signal RS from the terminal 11 is supplied to a timer 2 and an AND gate 5. The maximum permissible time during which the terminal can occupy exclusively a line 18 in this system is set in the timer 2 by a DIP switch 3. When the signal RS is active beyond this maximum permissible time, the timer 2 outputs an abnormality signal. This abnormality signal is supplied to the input terminal of the other side of the gate 5, and inhibits the signal RS, and the signal RS comes not to be supplied to a modulating/ demodulating part 6 as an active signal. Thus, the modulating/demodulating part 6 stops sending a carrier.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulation/demodulation device used in a multipoint communication system.

0002

2. Description of the Related Art Conventionally, a multipoint system has been known as one form of configuring a communication system. In this system, one CPU and a plurality of terminals (data communication terminal devices) are each connected to a modem, and each modem is connected by a communication line. A feature of this system is that since many terminals are connected to one line, line usage efficiency can be increased and cost performance is good. On the other hand, in this system, since many terminals share one line, there is a possibility that data collisions from the terminals may occur. Therefore, the CPU performs exclusive control of the line to prevent data collisions. However, in this system, if one terminal fails and that failure causes the transmission request to continue, the line remains exclusive to that terminal.
A problem has arisen in that other terminals cannot use the line.

Therefore, in recent years, a modem with a monitoring function is used to control the modem connected to the terminal that has fallen into the above state so that the transmission request signal (RS) is turned off as a troubleshooting measure. Modems with a monitoring function monitor multiple modems in the system and take countermeasures, which has the problem of taking time to respond and making it impossible to recover quickly.

0004

[Problems to be Solved by the Invention] As described above, in the conventional modem, if a terminal fails to continue transmitting a transmission request signal, the system recovers until the transmission request signal is turned off under the control of a modem with a monitoring function. The problem was that it was impossible to recover quickly.

[0005] The present invention was devised in view of the problems of the conventional modulation/demodulation equipment, and its purpose is to achieve quick recovery without relying on the control of other equipment even when a terminal continues to output transmission requests. It is an object of the present invention to provide a modulation/demodulation device that can perform the following functions. [Structure of the invention]

[0006]

[Means for Solving the Problems] The present invention receives a transmission request signal sent from a data communication terminal device and outputs an abnormal signal when the period during which the signal is active exceeds a period determined by the system. timer means for

00
[07] The modulation/demodulation apparatus is provided with transmission request signal inhibiting means for inhibiting the transmission request signal using the output of the timer means.

[0008]

[Operation] When the data communication terminal equipment fails to continue outputting the transmission request signal, the timer means which receives the transmission request signal outputs an abnormality signal. As a result, the transmission request signal is prohibited, and the modulating device operates as if the transmission request signal were turned off, and the monopolization of the line is stopped.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a multipoint communication system using a modem (modulator/demodulator) according to an embodiment of the present invention. In this system, CP
U10 is connected to modem 14, and terminals (data communication terminal devices) 11-13 are connected to modems 15-17, respectively. Modem 14 is connected to modems 15 to 17 via line 18 in a multipoint manner.

FIG. 1 shows the configuration of the main parts of the modem 15 (16, 17). The modem 15 has a terminal (DTE
) 11 gives various signals based on CCITT Recommendation X.21, and modem 15 gives various signals based on the same recommendation to the terminal 11. Of this signal, terminal 1
A transmission request signal RS sent from 1 is given to timer 2 and AND gate 5. The maximum allowable time for which a terminal can exclusively use the line 18 in the system is set in the timer 2 by the DIP switch 3. When the transmission request signal (RS) becomes active (H level) beyond this maximum allowable time, the timer 2 outputs an abnormal signal (L level) to the output 4, which is initially at the L level. This abnormal signal is given to the other input terminal of the AND gate 5, inhibits the transmission request signal (RS), and causes the modulation/demodulation section 6 to receive the transmission request signal (RS).
) is no longer given as active.

As a result of the above configuration, terminal 1
1 continues to output the transmission request signal (RS), the output of the AND gate 5 is initially at H level and the modulation/demodulation section 6
However, since the timer 2 outputs an abnormal signal after the above-mentioned time has elapsed, the transmission request signal RS is prohibited, which prevents the modulation/demodulation section 6 from transmitting the carrier. Stop.

Note that the means for setting the maximum allowable time for the timer 2 is not limited to the dip switch, but may also be a method of writing data to the timer.

[0014]

As explained above, according to the present invention, if a transmission request signal is made active and output from a terminal beyond a period determined by the system, this transmission request signal is prohibited, so that the carrier transmission is no longer performed, and communications of other terminals are no longer hindered in a multipoint communication system.

[Brief explanation of the drawing]

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

FIG. 2 is a configuration diagram of a communication system in which an embodiment of the present invention is used.

[Explanation of symbols]

Claims (1)

[Claims] 1. A timer means for receiving a transmission request signal sent from a data communication terminal device and outputting an abnormal signal when the period during which the signal is active exceeds a period determined by the system; A modulation/demodulation device comprising transmission request signal inhibiting means for inhibiting the transmission request signal using an output of the means.