Power Line Modem

14 EE March 1989 POWER LINE MODEM The NE5050 from Philips Components has been designed for sending and receiving data over the AC mains network, coaxial cables or twisted-pair cables. The modem described here is a mains-based application of the NE5050. It works in conjunction with an error-correcting computer program for exchanging data or remote control of equipment. A modem (acronym for MOdu- lator/DEModulator) is almost in- variably used where the distance between computers, or a computer and peripheral equipment, exceeds the capabilities of the well-known RS-232 interface with associated cables. In prac- tice, this means that some sort of modem is necessary when the data rate and distance exceed 1200 baud and about 30 metres respectively. In most cases, the modem is located physically close to the computer or peripheral (sometimes it is internal to it). Modems generally use frequency-shift-keying (FSK) of a carrier to convert the logic levels received from the computer"s RS- 2...