These are Burr Brown Devices from TI. The BB Chips are excellent devices and High Precision, but a bit more expensive. These can be used when customer demands a Higher Quality and Precision. These are good for High Reliability Industrial Instrumentation. – delabs
The XTR101 is a microcircuit, 4-20mA, two-wire transmitter containing a high accuracy instrumentation amplifier (IA), a voltage-controlled output current source, and dual-matched precision current reference.
The two-wire transmitter allows signal and power to be supplied on a single wire pair by modulating the power-supply current with the input signal source. The transmitter is immune to voltage drops from long runs and noise from motors, relays, actuators, switches, transformers, and industrial equipment.