Array Control Unit The ACU controls the overall behavior of the IUA It consists of the user-programmable CP and the uC The CP generates instructions to the uC, which in turn generates primitive CAAPP instructions Other functions may be performed by the CP as well
Antenna Control Unit - A PMAC dedicated to servo control and monitoring of the antenna azimuth and elevation drives, the chopping subreflector, holography, and the tension servo
Automatic call unit A device used with a standard modem to dial the telephone number for the originating equipment Dedicated ACU devices were popular (and necessary) before the advent of Hayes and Hayes-compatible modems ACUs work with asynchronous or synchronous modems