Siemens 6ES5 816-1BB11 Transmission Log Module

Siemens 6ES5-816-1BB11 Transmission Log Module is a dedicated interface module for SIMATIC S5 systems that attaches to a CPU 944 to log transmission data and events. In Siemens catalogs it appears as 6ES5-816-1BB11 (also listed as 6ES5-816-1BB11/21) and is described specifically as a Transmission Log Module for the CPU944 within the S5 family. This module supports the S5 transmission/logging subsystem, providing traceability of communications between the CPU and connected peripherals to support diagnostics, troubleshooting, and archival review. Availability is reflected across official Siemens references and third-party catalog listings, including variants marketed under 6ES5-816-1BB11 CPU944 Transmission Log Module.