Burr-Brown LDM70 Fully Isolated Limited Distance Modem

The Burr-Brown LDM70 is a fully isolated limited-distance modem that separates the host equipment from field wiring using optical couplers and a DC-DC converter, a design described by the manufacturer as providing complete isolation to prevent ground loops in rugged environments. It is powered from a 12 VAC supply (approximately 120 mA) and is specified with DC or AC input power, reflecting Burr-Brown's older implementation for field reliability. The modem offers a four-wire data link with DTR/RLSD handshake support and a maximum data rate of 57.6 kbaud, enabling reliable synchronous/asynchronous serial signaling over short distances. At the rated baud, the LDM70's practical distance is specified as up to 12 meters, making it suitable for controller-to-sensor connections within a single facility. As part of Burr-Brown's limited-distance modem line, the LDM70 emphasizes complete isolation rather than partial protection, distinguishing it from models that isolate only the receiver side.