4p4c Cat3 RJ Jack for Voice and Low-Speed Data
The Molex 0855135004 is a 4p4c (RJ9, RJ10, RJ22) jack from the 85513 series, rated Cat3. This jack is designed for voice-grade telecom, 10BASE-T Ethernet, and low-speed serial data links where the Cat3 frequency ceiling (16 MHz) is sufficient.
The Cat3 rating limits this jack to applications below 16 MHz — voice, 10BASE-T, and RS-232 over twisted pair. It is not rated for 100BASE-TX (Cat5) or higher data rates. The unshielded construction (no metal shell or grounding tabs) keeps the part simple and low-cost for non-critical signal paths, but it also means no EMI containment. If the build requires gigabit Ethernet or runs near switching supplies, step up to a shielded Cat5e or Cat6 jack in the same footprint class.
SMT Vertical Mount — Board Layout Fit
This jack is a vertical SMT part, so the plug inserts perpendicular to the PCB. The solder retention feature provides extra mechanical hold during reflow and against cable strain — useful for a connector that sees repeated plug/unplug cycles. The single-row, 1-port design keeps the footprint compact.
No official second-source or cross-reference is listed, but the 4p4c Cat3 jack format is a standard interface with multiple manufacturers offering pin-compatible parts — verify the footprint and solder pad layout against the board design before substituting.