The application of transistors to line communication equipment

The paper discusses the ways in which the use of transistors affects the design of communication transmission equipment for land lines. Transistors have many advantages over valves, but in order to exploit these advantages in practical equipment it has been necessary to wait for transistors of sufficient reliability. The first step is to design equipment which is compatible with existing valve equipment. In doing this, it is practicable with transistors to be much more free in the use of active circuits, and this makes possible new approaches to the design problems. A more important aspect is that with transistors new types of system become practicable. Battery operation of relatively complex equipment at unattended stations becomes possible. Very small, lowpower repeaters needing no buildings alter the balance between repeater cost and cable cost in the direction of cheaper cables with more frequent repeaters. Freedom in the use of active elements facilitates the use of the digital circuits needed for pulse systems. The prolific development of semiconductors makes it difficult to steer a reasonable course between making use of progress and restricting the number of types in use. It is likely that eventually the only active elements used will be semiconductor devices.