FIGURE. Principle of feedback signals.
If the computer sends a command signal to open a blend door in an automatic climate control system, a feedback signal may be sent back from the actuator to inform the computer the task was performed. The feedback signal will confirm both the door position and actuator operation (Figure 10-32). Another form of feedback is for the computer to monitor voltage as a switch, relay, or other actuator is activated. Changing states of the actuator will result in a predictable change in the computer’s voltage sensing circuit. The computer may set a diagnostic code if it does not receive the correct feedback signal.