ORIGINAL: Knife/edge

I would be very pleased if someone could help me. This is my first build of a model with a gas engine. Model A Sbach 342. with SAP 180. I would like to use a Rcxel kill switch. But I would like know if I can use 4.8v battery for ignition. And a 6v for receiver. Or do I have to use batteries of the same voltage, ie 4.8v or 6v. I must say I have no one in my club that help me. As no one else fly gas engined models. Most appreciated if somone can give me an answer. Knife/edge