To restore an SLC-500 processor to factory defaults: 1. Remove power and disconnect the battery from the processor. 2. For SLC-500 fixed I/O and models 5/01-5/02, short pins 14 and 28 on IC3 for 20 seconds using a paper clip or 10 ohm resistor. 3. For models 5/03-5/05, short the GND and VBB points for 60 seconds using a screwdriver after removing the CPU module and setting jumper J4 to protect. Restoring defaults will erase the ladder logic program and reset communications channels to default states.