Power module. A bi-polar unregulated 18V DC supply drives the system power buss through fused isolation diodes. Operates singly or as a redundant pair in the right hand positions of each RM100 rack frame. Front panel LEDs indicate low voltage on either buss or blown fuses. Power failure alarm relay contacts close for any power loss and can activate an external alarm. Alarm outputs from both PS100 positions are paralleled and brought to a barrier block (terminals 4 and 5) mounted on the left-hand rear of the card cage. Dual power transformers in each module run cooler and generate minimal hum field. DC lines are fully bypassed. AC line filtering, non-concentric wound power transformers and varistor clippers suppress power line transients and RF feed-through.