The 803 is a transistorised, bit-serial machine; the 803B has more parallel paths internally. It uses ferrite magnetic-core memory in 4096 or 8192 words of 40 bits, comprising 39 bits of data with parity. The central processing unit (CPU) is housed in one cabinet with a height, width, and depth, of . Circuitry is based on printed circuit boards with the circuits being rather simple and most of the signalling carried on wires. There is a second cabinet about half the size used for the power supply, which is unusually based on a large nickel–cadmium battery with charger, an early form of uninterruptible power supply. A third cabinet (the same size as the power cabinet) holds the extra working store on machines with 8192 word stores. There is an operator's control console, Creed teleprinter and high-speed paper punched tape reader and punch for input/output, using 5-track Elliott telecode code, not Baudot. Tape is read at 500 characters per second and punched at 100 cps.