A "momentary" switch is one that stays in the "ON" position only while being held there.
There are two switches on my MH that have an electrical symbol on them. One connects the house batteries to the engine starter, as motocross camper described. The other one, which holds position without keeping your finger on it, switches the in-dash radio/CD between house and chassis batteries.
Frank and Eileen
No longer RVers or FR owners