Relay unit for photoelectric sensor

A relay unit for photoelectric sensor that performs signal transmission between a photoelectric sensor and a communication master, the relay unit for photoelectric sensor comprising:

• a first terminal to which a first cable is connected between the first terminal and the photoelectric sensor;
• a second terminal to which a second cable is connected between the second terminal and a controller;
• a third terminal to which a third cable is connected between the third terminal and the communication master;
• a synchronization line which connects the first terminal to the second terminal and through which setting information and detection information of the photoelectric sensor is transmitted;
• a sensor-side communication controller configured to communicate with the photoelectric sensor via a branch line that branches off from the synchronization line;
• a master-side communication controller connected to and configured to communicate with the sensor-side communication controller and configured to communicate with the communication master via the third cable connected to the third terminal;
• and
• a storage unit,
• wherein the sensor-side communication controller acquires the setting information from the synchronization line and store the acquired setting information in the storage unit in response to reception of a backup instruction from the communication master by the master-side communication controller,
• wherein the sensor-side communication controller outputs the setting information stored in the storage unit to the synchronization line via the branch line in response to reception of a restoration instruction from the communication master by the master-side communication controller,
• wherein the sensor-side communication controller periodically or aperiodically compares the setting information transmitted through the synchronization line with the setting information of the storage unit so as to detect presence or absence of a difference, and
• wherein the sensor-side communication controller stores the setting information transmitted through the synchronization line in the storage unit in response to detection of the difference.