JPS61216560A - Protective circuit - Google Patents

Abstract

PURPOSE:To prevent occurrence of malfunction by preventing detection of a carrier from other data terminals unless the echo of the carrier generated by a transmitting data terminal at the time of completion of data transmission disappears perfectly. CONSTITUTION:A carrier detecting circuit 11 watches the carrier from each data terminal at all times, and when the carrier is detected, it drives a controlling circuit 13 and performs selective connection of data terminals. When the carrier detecting circuit 11 detects that the carrier disappeared with completion of communication, a delay circuit 12 operates, sends out a signal to the controlling circuit 13 after lapse of time sufficient for perfect disappearance of echo remaining in the system. Accordingly, the controlling circuit 13 operates and receives an output signal of the carrier detecting circuit 11, and performs selective connection of data terminals.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides selective control of which data terminal receives a call when a plurality of data terminals are connected via a telephone network, such as in a telephone conference. This is related to the problem when doing so.

In the above system, the conventional method has the drawback that when transmission from any data terminal ends, the center equipment mistakenly assumes that the transmission is in progress even though no other data terminal has made a transmission request. was strongly desired.

[Conventional technology]

FIG. 2 is a diagram showing an example of a conventional selection control circuit.

In the figure, 1 to n are data terminals, and 10 is a center device. The same symbols represent the same objects throughout all the figures below.

In such a case, the center device 10 connects each data terminal 1 to n.
The problem is how to process the outgoing signals from the terminals, but normally each data terminal 1 to n uses a carrier to send outgoing signals and data signals, and does not send out the carrier when not making a call, but when the terminal wishes to make a call. When doing so, send out this carrier.

The center device 10 constantly monitors carriers from each data terminal 1 to n, detects the carrier that arrived earliest (for example, the carrier from data terminal 1), and
.

In this case, each data terminal 1 to n uses a hybrid to separate the two wires and four wires, so even if the carrier of data terminal 1, which has been transmitting up until now, disappears, its echo will still be transmitted to the data. When the center device 1O returns from terminals 2 to n, it mistakenly assumes that a call has been made from a data terminal that is not making the call, and enters into communication with that data terminal.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional systems and to provide a protection circuit that prevents center equipment from misrecognizing an echo and assuming that it is transmitting.

[Means for solving problems]

Means for solving the problem includes accommodating a plurality of data terminals via a telephone network, and transmitting the transmission request signal transmitted from one of the data terminals transmitting the transmission request signal. In a system for detecting data signals from the data terminal and broadcasting connection to the other data terminals, after the detection circuit detects the completion of data transmission from the transmitting data terminal, the data signals from the other data terminals are connected for a certain period of time. This is achieved by suppressing the detection of transmission request signals.

[Effect]

According to the present invention, the transmitting data terminal does not detect carriers from other data terminals unless the carrier echo generated at the end of data transmission completely disappears, so there is no malfunction.

〔Example〕

FIG. 1 is a diagram showing an embodiment of a protection circuit according to the present invention.

In the figure, 11 is a carrier detection circuit, 12 is a delay circuit, and 13 is a carrier detection circuit.
is the control circuit.

The present invention will be described in detail below with reference to the drawings.

According to the present invention, the delay circuit 12 is provided on the output side of the carrier detection circuit 11 of the conventional center device 10.
The control circuit 13 is driven by the output.

The carrier detection circuit 11 always monitors carriers from each data terminal 1 to n as in the conventional circuit, and when a carrier is detected, it drives the control circuit 13 to selectively connect the data terminals described above. When the carrier detection circuit 11 detects that the echo has disappeared, the delay circuit 12 according to the present invention operates and sends a signal to the control circuit 13 after a period of time sufficient for the echo remaining in the system to completely disappear.

Therefore, the control circuit 13 operates, receives the output signal of the carrier detection circuit 11, and selectively connects the data terminal as in the conventional case.

(Effects of the Invention) As described above in detail, the present invention has the great effect that the center equipment does not malfunction due to carrier echo.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a protection circuit according to the present invention. FIG. 2 is a diagram showing an example of a conventional selection control circuit. In the figure, 1 to n are data terminals, 10 is a center device,
11 is a carrier detection circuit, 12 is a delay circuit, and 13 is a control circuit.

Claims (1)

[Claims] A plurality of data terminals are accommodated through a telephone network, and the transmission request signal transmitted from one of the data terminals that is transmitting the transmission request signal is detected, and the data signal from the data terminal is detected. In the system for broadcasting connection of the data terminal to the other data terminal, the detection circuit suppresses detection of the transmission request signal of the other data terminal for a certain period of time after detecting the end of data transmission of the transmission data terminal. Features a protection circuit.