The Allen-Bradley 1746-RT28 is a removable terminal block which is used with the following terminal modules on Allen-Bradley PLCs: the 1746-NI4, -NIO4I, and -NIO4V analog input/combo modules. PLCs are computers specifically designed for controlling plant machinery. PLCs get inputs from plant machinery e.g. drives. Programs running in the PLCs then drive outputs based on the inputs. The input and output signals can be either analog or digital signals and can also be used to drive relays.

Removable Terminal Blocks (RTBs) are terminal blocks which can be attached to and removed from the I/O modules. Physical wiring for input and output signals terminates on the terminal blocks.

The inputs and outputs are provided via I/O (input/output) terminal modules. Dedicated modules for inputs and outputs are available. Additionally, combination modules are also available which can be used for both inputs and outputs. A maximum of four I/O can be connected to a single 1746-RT28 module. The contacts are gold-plated to ensure maximum conductivity.

The benefit that the removable terminal blocks offer is that faulty I/O modules can be replaced without needing to be rewired. The design of the removable terminal block with its I/O modules separate from the terminal blocks ensures fast troubleshooting. It also keeps down the cost maintenance and the number of necessary spare parts.

A color band on the front of the 1746-RT28 module aids in matching the correct type of removable terminal block to the correct type of I/O module. Each terminal block comes with self-lifting pressure plates that allow for secure wiring. Furthermore, each terminal block has barriers on 3 sides to prevent accidental shorting of wiring.