Siemens 6ES7921-3AA20-0AA0 SIMATIC TOP Connect Front Connector 40-Pole Spring PLC Connection Module

The Siemens 6ES7921-3AA20-0AA0 is a SIMATIC TOP connect front connector module that replaces the standard 40-pole front connector on S7-300 digital I/O modules wired for 32 channels. It routes signals through two 16-pole IDC cable connections and feeds power through spring clamp terminals rated 24 V DC, 1 A per contact. It plugs directly into the module in place of the factory connector.

Technical Specifications

Certifications & Standards

• cULus

Selection Notes

The 40-pole count matches I/O modules wired with two 16-pole IDC cables, so it fits 32-channel digital modules rather than the 16-channel versions that only need a 20-pole connector. Spring clamp terminals let the L+/M potential-feed wiring be connected without a screwdriver, which speeds up cabinet builds where several of these modules sit in a row; choose the screw-terminal version instead where the panel spec calls for a checkable torque value on the supply connection.