B&B Electronics CL251 RS-232 to Current Loop Converter

The B&B Electronics CL251 is a compact RS-232 to 20mA current loop signal converter designed for industrial serial communications applications. It enables reliable data transmission between RS-232 devices and equipment using the 20mA current loop interface standard — a legacy protocol widely used in industrial automation, process control, and teletype (TTY) environments.

Key Features:

• Converts RS-232 signals to 20mA active or passive current loop
• Supports full-duplex serial communication
• Compact, DIN-rail or panel-mountable form factor
• Designed for industrial environments with wide operating temperature range
• No external power required for active loop configurations (self-powered from RS-232 line)
• Compatible with standard RS-232 serial ports on PCs and industrial controllers

The CL251 is ideal for integrating older current loop peripherals — such as printers, terminals, and PLCs — into modern RS-232-based systems. Its rugged construction and passive component design ensure long-term reliability in demanding industrial installations.