The Comprehensive BNC Male to RCA Female 5-Pack Adapter Kit from B&H includes five BNC male to RCA female adapters for plugging RCA cables to BNC inputs.
One reason for using these adapters is being limited to one or the other type of connector. Another reason is safety -- accidentally yanking out an RCA cable will in most cases simply just pull the cable out, but a BNC cable will pull the connected device along with it.
The RCA female ends accept RCA male inputs.
5 x Comprehensive PJ-BP Male BNC to Female RCA Adapter
The Comprehensive PJ-BP is a male BNC to female RCA adapter for joining a BNC socket with an RCA plug.