A New Local Video Transmission System

The A2A system is a new broadband wire transmission system for providing television connecting circuits over short distances. The system provides video transmission for frequencies up to 4".5 rac over balanced pairs designed for such use. Its design is predicated on meeting high quality performance objectives for a 4,000 mile network, which may comprise a number of A2A circuits along with intercity television systems of other types. Television connecting circuits are used for a variety of purposes in network operations. Some examples of these uses are illustrated by the diagram of Fig. 1. Large broadcasters usually have their studios, master control, and broadcast transmitter distributed among several buildings in various locations in a city or metropolitan area. The A2A system furnishes broadband tielines to interconnect these facilities. Two-way con677 678 T H E B E L L SYSTEM T E C H N I C A L J O U R N A L , JULY 1955 nections between the master control location and the studio are often required for programming purposes. For example, filmed material from the master control location may be sent to the studio, there to be combined with the live program and returned to the master control over a second circuit. For local broadcast transmission a third circuit to the radio transmitter is required. For network operation, connecting circuits are required between the master control and the central switching point where connections to the intercity coaxial or microwave radio systems are made.