The L-3 Avionics TRC-899 Transmitter Receiver Computer is part of the L-3 Avionics SKY899 Skywatch HP System which can be installed as a TAS or TCAS I active surveillance system. The TRC-899 converts signals from a directional antenna as well as from other aircraft systems into an on-screen picture of intruder aircraft locations, and if necessary, aural traffic advisories. The TRC-899 can track up to 35 intruder aircraft simultaneously, but only displays the 8-12 most threatening intruders being tracked (number displayed depends on the display installed).

The TRC-899 is 3.56 inches wide, 12.52 inches deep, 7.62 inches high and weighs 9.00 pounds without a mounting tray. The TRC-899 can be operated up to an altitude of +55,000 feet within an operating temperature of -55°C to +85°C. The TRC-899 is conduction and forced air convection cooled via an internal fan. The TRC-899 has a maximum tracking range for ATCRBS surveillance of 35 nmi but a maximum of 50 nmi for ADS-B surveillance with a relative altitude tracking range of ±10,000 feet maximum.