Agilent Technologies HP 8719D Service Manual page 351

The processed and formatted data is llnally routed to the display, and to
the HP-IB for remote operation. Refer to "Digital Control Theory" in this
section and to Data Processing in the tirst chapter of the Reference for more
information on signal processing.
An additional input to the A10 assembly is the analog bus (ABUS), a built-in
service tool for testing analog circuits within the instrument. This is a single
multiplexed line that networks analog nodes throughout the instrument, or
monitors an external input at the rear panel AUX INPUT connector. It is
controlled by the CPU, and used like an oscilloscope or frequency counter to
make internal voltage and frequency measurements.