The exchange used reed relays as the switching medium, and the reeds themselves were approximately 3 inches in length and the only ones available. They were provided by the Hivac subsidiary of AT&E (then the only UK manufacturer of reed inserts.) It had multi-stage switching divided into A, B and C switches, interconnected by links. A typical local call would be connected via A-B-C-Link-C-B-A. Links could each either have or not have transmission bridges for local calls. The bridges were contained within the outgoing junction units.