8-bit number including the sign. These lines are updated at the rate of 9.27 volts per 32 word times. The range is + 10 volts with an accuracy of ± 200 mv. Single Character - The single character output provides four-bit characters suitable for typewriter, tape punch or other similar output equipment. A parity check bit and two timing bits are issued automatically with each character. Cable - The cable output is a serial message of up to 96 bits in length transmitted from the four word C-loop. The maximum data rate is 1600 bits per second* The operation is begun by execution of the Enable Cable Output (ECO) instruction and proceeds basically independent of program control. Binary - There are four pairs of outputs which can be used to control external equipment such as gyro, etc. The output states are automatically updated under program control every 10 MS. The output is in the form of +1 or -1. Telemetry - A timing signal is issued under program control which signifies that the accumulator contains information which is to be read by the external equipment receiving the timing signal. Miscellaneous - These signals include Parity/Verify error signal, mode indication and stage reference. Memory Unit The D-37C computer memory consists of a rotating magnetic disk driven by a synchronous motor at 6000 rpm. Adjacent to the disk are two fixed head plates which house the read and write heads. The disk has a thin magnetic oxide coating on both sides for storing information. This disk is supported by air bearings generated by the rotating disk. The disk is divided into tracks or channels of 128 words each for main memory. A total capacity of 7222 words may be contained in the 56 channels of 128 Sectors, six 4-word loops, one 8-word loop, one 16-word loop and six 1-word loops. Programming The computer uses a full 24-bit instruction word and data word. Data is represented in one of two fashions, as a 23-bit binary fraction (full word) or as a 10-bit fraction (split word). The two formats are shown in the figure. Instructions also have two formats, either flagged or unflagged as indicated in the figure. A list with all of the available instructions with numeric and mnemonic codes follows. For more information on programming see: Kee, W. T. Programming Manual for the D-37C Computer. Anaheim, California, Autonetics, Division of North American