Asleep at the switch

Hi! My mom thinks this comes from the old railroad days. Is she right? Can you please tell me the meaning and origin? Thank you. Sax

I think mom is right. I've usually heard it as "asleep at the switches." It describes someone who invites disaster by failing to pay attention on the job. An engineer who fell asleep instead of tending to the switches (controls) in the cab of a train would cause a wreck.