> BC-345 or BC-453? I'm sure he meant BC-345-A, which is a pretty commonly used switch box for the FL-5-A range filter. Part of RC-32. These early filters did not contain a built-in switch like the FL-8-A does. It would likely be just as likely that a P-40 would use the FL-8-A instead of the FL-5-A plus BC-345-A. Mike / KK5F