normally PCB mount relay (suger cube type) are called 1 change over or 2 change over type relays
they have 5 or 8 connections – terminals
in 1 C/O type relay there are 5 terminals. 2 for coils and 3 for C, NC and NO
from these one of the coil terminal is connected to +Ve supply, second is connected with collector of transistor
C, NC and NO are for connecting device or load