Model 621-1550 24 Vac/Vdc Discrete Input module

A separate connection to L1/+Vdc is needed when the module is used in an ungrounded ac control circuit. Input operation is unaffected by this connection. However, for ungrounded ac systems using ground fault detection circuitry, this connection balances the system and prevents erroneous ground fault indications.

The ‘R’ suffix indicates the module can be removed or inserted into an I/O rack while the rack remains powered. Other I/O modules in the rack continue to control the machine or process.