TL;DR - A multi-gig RJ45 jack is the same 8P8C socket as Gigabit, but the magnetics have to hold up at higher frequency. Match the rate to the cable and don't reuse a Gigabit-only magjack at 5G.
- Standards: 2.5GBASE-T + 5GBASE-T = IEEE 802.3bz (NBASE-T). Down-clocked 10GBASE-T (PAM-16 + LDPC).
- Cabling: 2.5G -> Cat5e (100 m). 5G -> Cat6 (100 m). 10G -> Cat6A.
- Why the jack changes: 5G pushes energy to ~200 MHz. A Gigabit-only magjack characterized to ~100 MHz can lose return-loss/crosstalk margin. Same footprint (IEC 60603-7), different qualification.
- Isolation stays: 1CT:1CT per pair; integrated jacks keep the 1500 Vrms / 2250 VDC hi-pot, higher Vrms tiers for industrial.
- Selection axes: integrated magnetics vs discrete, SMT vs DIP, port count, PoE tier (to 4PPoE), isolation (1500-5000 Vrms).
- VOOHU magjack build: PBT UL94 V-0, C2680 nickel-plated shield, C5210 phosphor-bronze contacts, 6 uin gold, >=750 mating cycles, <=23 N.
Checklist: rate-to-cable, integrated vs discrete on board area, PoE thermal headroom, verify return-loss/NEXT at 200 MHz for 5G.
Full write-up (spec table + FAQ) from VOOHU: https://voohuelectronic-ux.github.io/voohu-rj45-guide/resources/multi-gig-2-5g-5g-rj45-jacks.html
VOOHU Electronics - https://www.voohuele.com - olivia@voohuele.com - WhatsApp +86 133 5804 1040
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