1756-TBCH module you mentioned is a Terminal Base Connector (TBC) module used in Allen-Bradley ControlLogix® programmable logic controllers (PLCs) from Rockwell Automation. This module provides a connection point for the I/O modules in the ControlLogix chassis.

The 1756-TBCH module is designed to be used with the 1756 chassis system, which is the rack-based platform for the ControlLogix PLCs. It serves as a communication hub between the I/O modules and the backplane of the chassis, allowing data exchange between the modules and the PLC processor.

The module provides a removable terminal block for easy wiring of field devices to the I/O modules. It supports a variety of I/O modules, including digital input/output, analog input/output, and specialty modules, which can be installed in the same chassis.

The 1756-TBCH module features a robust design to withstand industrial environments and provides reliable communication between the I/O modules and the PLC. It offers a high-speed backplane communication and can handle a large number of I/O points, making it suitable for a wide range of automation applications.