Masprodenkoh Kabushikikaisha

Eiji Shibata

Toshihiro Sugiura

In a cable broadcasting system of the invention capable of setting output or stop of broadcasting-signals from tap output terminals of a tap device in response to a command signal transmitted by a center equipment, when demand for output setting for many tap devices occurs, output setting of the corresponding tap devices can be surely carried out without increasing the load on each power supply device for supplying the tap devices in each district with electricity. When demand for setting tap output of plural tap device occurs, a head-end controller reads output setting data for all the tap devices which are the objects of tap output setting and transmits command signals in order to tap devices at a rate of one tap device per each district covered by a power supply device. The interval of transmission of command signals to one district is controlled to be longer than or equal to the time &#x394;tn necessary for the tap device to which a command signal was previously transmitted to finish tap output setting operation.

Cable broadcasting system

A part of transmission signal is branched by a directional coupler, and split by a splitting circuit, so that the transmission signal can be outputted to the subscribers' terminal devices via branched output terminals. Latching relays disposed in signal paths to the branched output terminals from the splitting circuit can set the output/stop of the transmission signal to the terminal devices. A control circuit switches the connected/disconnected state of the relays in response to the command signal from the center apparatus. When an operation switch is turned on, all the relays are placed into the connected state. As a result, after the installation of the tap device, by operating the operation switch, the broadcasting signal can be distributed to the terminal devices before the command signal is received.

Tap device of cable broadcasting system

An electronic device for distributing broadcast signals in a cable broadcasting system includes a receiving circuit receiving broadcas signals including command signals and a microcomputer for controlling the electronic device according to the command signals. A watchdog timer counts an output s op period and compares with abnormality determining times. An output stop period is reset by a microcomputer pulse signal generated at constant intervals and representing normal operation of the microcomputer and an input stop period is reset by a periodic command pulse representing normal operation of the input from the receiving circuit to the microcomputer. The timer generates a microcomputer eset signal when a stop period exceeds an abnormality determining time.

Electronic device for cable broadcasting system

In a proposed cable broadcasting system in which a command signal transmitted from a center equipment to a transmission line for setting an operation mode of a tap device on the transmission line, the command signal can be transmitted without fail even when an instantaneous power failure occurs because of thunderbolt and the like. The center equipment transmits a command signal with a retransmission number indicating the number of transmission plural times at intervals of a time longer than the duration time of the instantaneous power failure. The tap device determines whether the new received data of the command signal is a command to the tap device itself by using the address of the received data. When the command is for itself, it is determined whether the command (received command) coincides with the command previously used for setting the operation mode. When they do not coincide with each other, the operation mode is set in response to the received command. To the contrary, when they coincide with each other, the retransmission number given to each command is compared. When the retransmission number of the received command is equal to or smaller than the previous number, the operation mode is set in response to the received command.

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Nisshin, Japan

Eiji Shibata