Abstract: This invention provides improved methods of protection required under the 1999 edition of the National Electric Code, section NEC 830 requirement that if a drop coaxial cable (usually supplying an individual residence) carries power above a certain voltage, it must include sufficient protection from electric shock for people who may come in contact with it. A drop coaxial cable would be carrying sufficient power for NEC 830 protection if it were supplying a cable telephone interface box or other AC powered network interface devices. In one embodiment, the invention utilizes the AC power signal from the drop cable to operate an AC power sensing circuit. The circuit utilizes an upper and lower current range to determine whether to activate a switch operative to interrupt the AC power in the drop cable. One variation of the invention utilizes an oscillator generated probe signal to determine if there is a valid circuit connection.

Abstract: A power supply includes a control circuit that inhibits excessive input current draw during a low-line condition by decreasing a power supply output voltage in response to a measured change in either power supply input voltage or power supply input current. The power supply may be, for example, a cable television distribution network power supply that receives power from the coaxial cable that carries the television or other media signals or, in the case an optical fiber network, an auxiliary power cable associated with the fiber cable that carries the media signals.

Abstract: A method and apparatus providing for a multifrequency receiver with upstream switching of received frequencies. The invention is described in connection with a cable plant having a plurality of modems transmitting at a first frequency. It may be desirable to locate a second frequency having more desirable transmission characteristics and to cause the modems to transmit at the second frequency. It is disclosed to utilize an additional receiver coupled through a switch which may be used to both locate a desirable frequency and to facilitate automatic switching of the cable modems from the first frequency to the second frequency.

Abstract: Active and spare circuit cards are each paired with switch cards. Each switch on the switch cards is daisy chained with prior and succeeding switches. A master controller senses a faulty circuit indication signal from each of the active circuit cards. When the faulty circuit indication signal indicates a fault on a particular active circuit card, the controller instructs the switch card that is paired with that circuit card to switch it out and switch in a spare circuit card.