CR1 stands for what?

• A. Central Router 1
• B. Control Relay 1
• C. Control Register 1
• D. Circuit Relay 1

Answer: (B)

In control circuits and instrumentation diagrams, the prefix CR is used to label a Control Relay, which is a relay used to actuate or control a portion of the circuit. CR1 simply identifies the first control relay. This device takes a relatively small control signal and energizes a larger circuit, providing isolation and enabling logic control within the system. The other terms don’t fit NRCC labeling conventions: Central Router denotes a network device, not a control relay; a Control Register refers to a memory element rather than a relay; and Circuit Relay isn’t a standard NRCC label. So the intended meaning is that CR1 is a Control Relay.