What does the heartbeat functionality mean?

To actively track if the in-line appliance connected to the Bypass TAP is operational, the TAP uses bidirectional and configurable heartbeat packets with the data stream. In turn, these heartbeat packets need to be forwarded by the in-line appliance. But, if the in-line appliance is compromised in any way, these packets will no longer be returned to the Bypass TAP. To ensure that the critical network link stays up, the TAP will enable bypass mode.