Heartbeat signal

Electric power system
Heartbeat signals are the regularly repeated signals generated by hardware, software, or firmware to indicate normal operation or for synchronization with other components within an energy delivery system. }}

Overview
"Heartbeat signals can be configured in the hardware, software, or firmware. If a heartbeat signal is not received in the prescribed time, it is an indication that the component generating the signal is not operating within its normal parameters. Heartbeat signals can be sent over serial connections or routed protocols. Problems may arise when heartbeat signals or protocols are corrupted, spoofed, or possibly used as an entry point for unauthorized access."