hi if the control for base is around 12 mA and the switch is to switch on a relay what is can the circuit be

 

Welcome to the forums.

You don't give nearly enough information. What is the transistor, the relay coil voltage & current? What is the current gain figure for the transistor - hint - that gives you your answer.

 

Are you asking for a schematic for the transistor-relay coupling? Can you be more specific? What are you voltage-current needs?