Siemens 6ES7-138-4FR00-0AA0 is a four-channel digital relay output module for the ET 200S distributed I/O system, delivering four F-RO (fail-safe relay output) contacts for PROFIsafe applications. The module provides isolated relay outputs that switch external loads from a 24 V DC control signal. With dimensions of about 160 × 30 × 80 mm, it also includes an address area and diagnostic LEDs to aid configuration and monitoring. It is used to interface field devices requiring isolated relay control within ET 200S installations.
