The Siemens 3RK1903-1CB00 is a PM-X accessory module from the Local Safety Modules line, designed specifically for safety circuits. It serves as a motor starter connection module rated up to safety category 4 per EN 954-1, handling the feedback circuit and infeed protection in a safety-related control system. This module operates on a 20.4 to 28.8 V DC control supply and supports bus communication, making it suitable for integration into a networked safety architecture. It does not include integral short-circuit protection, so upstream protection must be provided in the panel design. Physically, it measures 30 mm wide, 196.5 mm tall, and 117.5 mm deep, and is designed to be plugged onto a TM-X15 S27-01 base module.
No UL, CSA, or CE listing is explicitly recorded in the available documentation, so verification against local code requirements is the integrator's responsibility.