B&B Electronics CL21 RS-232 to 20mA Current Loop Converter

The B&B Electronics CL21 is a passive RS-232 to 20mA current loop interface converter designed for reliable serial data communication in industrial environments. It allows devices equipped with standard RS-232 ports to communicate over a 20mA current loop connection — a legacy serial standard commonly found in older industrial equipment, terminals, and teletype devices.

Key Features:

• Converts RS-232 signals to 20mA current loop (and vice versa)
• Passive design — powered directly from the RS-232 port, no external power supply required
• Supports full-duplex communication
• Compact form factor suitable for panel mounting or inline use
• Rugged construction for industrial deployment
• Compatible with a wide range of RS-232 host equipment including PCs, PLCs, and industrial controllers

The CL21 is an ideal solution for integrating legacy current loop devices into modern RS-232 systems, extending the life of existing equipment without costly hardware replacement. Manufactured by B&B Electronics Manufacturing Company, a trusted name in industrial serial communication and connectivity products.