FEEDER SWITCH FOR A BIDIRECTIONAL CABLE TELEVISIONFEEDER SWITCH FOR A BIDIRECTIONAL CABLE TELEVISION SYSTEM SYSTEM

摘要

A two-way cable television (CATV) system includes a cable for transmitting television signals downstream (from a headend to a subscriber) in the VHF frequency band, and for transmitting signals upstream (from the subscriber to the headend) in the frequency band below VHF. A feeder switch is series-connected with the cable through a pair of input/output ports. These ports are normally interconnected by a high pass filter to preclude the transmission of electrical signals in the upstream frequency band. However, circuitry within the feeder switch detects upstream transmission and, in response, replaces the high pass filter with a direct connection between the ports to enable both upstream and downstream transmission. Since each subscriber is connected to the cable via the feeder switch, thermal noise does not accumulate in the upstream direction from subscribers (most of them) who are not presently transmitting.