The 26m antenna drives are Baldor 18H variable speed drives controlled by the drive PC, sys26m. Sys26m is a 486 computer with lots of parallel I/O, analog I/O to command the speed to the Baldors. It looks after the axis encoders, and measures where the telescope is pointing. It keeps track of the UT and sidereal time in order to achieve correct telescope pointing. It displays the coordinates in RA/DEC as well as UT and sidereal time on displays in the control room, and the office. It is located in the room under the antenna, but it has a repeat breakout box in control room rack 2. This breakout panel has a reset button which occasionally needs to be pressed. The UT and RA/Dec displays at the top of rack 1 need to be updating. If not you need to press the reset button in rack 2 breakout panel.
The drive PC, sys26m, accepts coordinates from the field system computer and the other observing computers and sends the antenna off to the right position. It reports back when it arrives and keeps its own daily log for a month.
If the antenna is stuck/not responding to commands, or the co-ordinate displays in rack 1 aren’t updating, then the problem is probably with the drive pc and it needs to be rebooted. This is particularly important since this pc also measures wind speed, and if it isn’t working, the dish will not automatically stow in the case of high wind - potentially very costly!