Mal, when the cable cars were first set up we used a custom built timed reversing unit fitted to the original motor. Time intervals were random and varied between 10 seconds and five minutes. This unit worked well for about five years and then gave up the ghost. We tried to source a suitable replacement without much luck, so we reverted to manual reversing using a toggle switch to change polarity and direction. This set up has been operating for ten years. In fact the entire power unit has been in use for the last sixteen years.