The Allen-Bradley 1771-A4B is a universal I/O chassis that is part of the 1771 Programmable Logic Controller (PLC) product family. This chassis features Sixteen (16) I/O slots, which hosts the electronic circuitry, specifically the backplane, for distributing power to the attached modules. It also hosts the hinges for field wiring arms.

The 1771-A4B is designed to be operated at a temperature range of 32-140 Degree Fahrenheit or 0-60 Degree Celsius while the hardware’s storage temperature is -40 to 185 Degree Fahrenheit or -40 to 85 Degree Celsius. It has a relative humidity of 5-95% noncondensing. When installing this universal I/O chassis, maintain panel vibration and shock within 2g at 10-500 Hz and 15g, respectively.

The 1771-A4B is capable of receiving power via 1771 processor with integral power supplies that provided 2-4 Amperes, power supply modules with rated output of 3-8 Amperes and external power supplies with output Current of 6.5-16 Amperes. As a general rule, never install an external power supply and a power supply module to the 1771-A4B. This power supply connection is not compatible and will disqualify the hardware configuration.



The 1771-A4B chassis has 16 I/O slots. It has dimensions of 12.4 x 24 x 7.6 in. and weighs 14.8 lbs. For installation in a 1771 PLC-5 system, it uses the back-panel mounting method with adequate spacing and an open enclosure. The chassis backplane has a power supply of 8A at 5V DC.

The 1771-A4B chassis has a universal configuration for chassis mounting and system design because of its own consistent design. 1771 I/O modules are small, flexible, cost-effective, and provide a complete range of digital, analog, and intelligent I/O modules for various applications. I/O modules come with wiring arms and remote termination panels, eliminating the need for disconnecting the wire to replace the module. For troubleshooting and diagnostics, status indicators are present on the front of the modules. For future expansion, it can be easily replaced with a larger chassis. It is intended for use in an industrial environment with a 0 - 60 °. Celsius (32 - 140 deg. Fahrenheit) operating temperature, 5-95 % noncondensing relative humidity, and a 30g operating shock.