3-1939755-6 is a 4mm receptacle board-to-board connector designed for vertical parallel stacking applications in Computer-on-Module (COM) systems. This legacy 8GT/s connector features a 0.5mm double-row contact pitch with 220 positions and 30µ" gold plating for reliable signal transmission. The connector is designed for surface mount (SMT) PCB termination and operates over a temperature range of -45°C to 125°C with 85 Ohm impedance. It is commonly used in COM Express Type 7 connections between COM and solution boards, as well as industrial machinery, test and measurement equipment, and medical devices where vertical parallel board-to-board connections are required.