Digits A and B of the ID word are a predetermined bit pattern specifying the type of DLP. Digits C and D of theID word are a bit pattern specified by field-installed jumpers, and are used to uniquely identify the DLP. The ID word for the DLP is formatted as follows: ##STR1##I/O DESCRIPTORSThe I/O descriptor is transmitted in 17 parallel bits including odd parity.