The Texas Instruments SN65HVD55DG4 is a full-duplex RS-422/RS-485 transceiver in a 14-pin SOIC package, designed for differential data buses up to 1 Mbps. Full-duplex means separate twisted pairs for transmit and receive, so the bus can talk and listen at the same time — useful for multi-drop polled networks or point-to-point links where you need simultaneous bidirectional traffic without a direction-control pin. If your microcontroller is 3.3 V, the logic input thresholds are 5 V-tolerant on the driver side, but the receiver output will swing 0 V to 5 V — you need a level translator or a 5 V-tolerant input on the MCU side. The receiver hysteresis is 50 mV, which gives clean switching on a noisy bus without external schmitt triggers.
The SOIC-14 footprint is a standard 3.90 mm wide body. Surface-mount only; no through-hole option. The 'DG4' suffix indicates the tube (rail) shipping medium, but the part is also available in tape-and-reel as the 'DR' variant if your pick-and-place line needs reels.
TI lists the SN65HVD55DG4 as Active (current production).