The Siemens 3TX4001-2A is an auxiliary relay with normally closed (NC) contacts. It is typically used in conjunction with control devices like contactors and circuit breakers to provide additional switching capabilities. The relay is designed for applications that require a control circuit to open or close a contact in response to specific conditions, such as for signaling or interlocking purposes. The 3TX4001-2A offers reliable and durable performance, and its compact design makes it suitable for integration into industrial control systems and automation circuits.