We were running a FIS race and had completed 8 timed runs when the S4 display showed END. This message had come up previous occasion during startup for time of day use witht the P5 connected. By disconnecting the P5 during startup, I eliminated the problem. But we ended up running the FIS race without a printer on the primary. Do we need an external power supply for the P5 to avoid the problem?

Yes. The P5 requires a 12v power supply to the S4. This can either be an ALGE PS-12, NLG13, NLG8, or Radio Shack type supply. Pin 3 is ground, pin 4 is power input on the 5 pin din connector. The red LED will light up when correct.