An RJ45 jack — the female modular socket (母座) the cable plug mates into — hides a surprising amount of engineering behind a short datasheet. Choose the wrong line and the port fails EMC, cooks under PoE, will not fit the enclosure, or drops link at 2.5G. This guide reads the RJ45 jack datasheet the way a hardware engineer does: what each spec means, the value to expect, and the standard behind it — with real options drawn from VOOHU's jack range and parameters sourced from IEC 60603-7, ANSI/TIA-568 and IEEE 802.3.
Every RJ45 jack datasheet is a table of the same fundamental lines, whether it comes from VOOHU or any other maker. The reference below groups them, explains what each tells you, gives the value or option to expect, and names the governing standard. VOOHU's own product filter exposes these exact selectable attributes, so the "VOOHU option" column reflects real catalog choices, not invented values.
| Spec line | What it tells you | Typical value / VOOHU option | Standard / source |
|---|---|---|---|
| Data rate / category | Top Ethernet speed the contact geometry is qualified for | 10/100M, 100/1000M, 2.5G, 5G, 10GBASE-T (and HDBaseT) | IEEE 802.3 · ANSI/TIA-568 |
| Integrated magnetics | Whether transformer + common-mode choke + Bob-Smith are built in (magjack) or external (discrete) | Yes (SYT magjack) / No (discrete base) | IEEE 802.3 |
| Ports / gang | Port matrix and stacking of the housing | 1×1 to 1×8, 2×1 to 2×8 | — |
| Tab orientation | Latch/spring up or down — sets front- or back-of-board mounting and shell window | Tab-Up / Tab-Down | — |
| Body angle | Cable exit relative to the board | 45° / 90° (right-angle) / 180° (vertical) | — |
| Mount | How the jack attaches to the PCB | DIP (through-hole) / SMT | IPC J-STD-020 (reflow) |
| Shielding | Metal shell for EMC/ESD, plus Bob-Smith/ground path | Shielded (STP) / Unshielded (UTP) | — |
| PoE current rating | Max continuous DC per contact when pins carry power + data | non-PoE, 350/600/720/850/900/1000 mA, 1.5 A | IEEE 802.3af/at/bt |
| Operating temperature | Ambient range the jack is rated to | 0~+70 °C (commercial) … −40~+85 °C / −40~+105 °C (industrial) | VOOHU RJ45 range |
| Contact plating | Gold-over-nickel thickness on the mating area | 6 / 15 / 30 / 50 µin (0.15 / 0.38 / 0.76 / 1.27 µm) | Industry plating tiers |
| Durability | Rated mating cycles (plug insertions) | ≥ 750 cycles | IEC 60603-7 |
| Contact resistance | Low-resistance quality of the contact interface | ≤ 20 mΩ | IEC 60603-7-class |
| Insulation resistance | Leakage between adjacent contacts / to shell | ≥ 500 MΩ | IEC 60603-7-class |
| Dielectric withstanding (DWV) | Connector insulation breakdown margin | 1000 V AC, 1 min | IEC 60603-7-class |
| Isolation (magjack Hi-Pot) | Primary-to-secondary barrier of the built-in magnetics | ≥ 1500 V rms | IEEE 802.3 |
| LED indicators | Optional bi-color Link/Activity light guides | No-LED or combos (G/Y, G/O, G/G …) | — |
These lines rarely change the electrical class, but get one wrong and the board comes back. Ports/gang (1×N, 2×N) drive board utilization and pin-header coplanarity — larger 2×N modules are more prone to reflow warping, so look for positioning posts. Tab orientation (up/down) decides whether the jack mounts on the front or back of the PCB and which way the shell window faces. Body angle — 45°, 90° right-angle or 180° vertical — plus offset/sink-type and low-profile variants set the Z-height; sink-type jacks drop into a board cut-out to shrink the enclosure but consume edge routing. Mount is DIP (through-hole, strongest against plug-in force) or SMT (automation-friendly, add board locks). See our companion guides on THT vs SMT mounting and tab-up vs tab-down orientation for the full trade-offs.
The data rate / category is the headline: an 8P8C jack is qualified as a component to a TIA category by meeting the connector NEXT (near-end crosstalk) and return-loss limits at that category's bandwidth. The channel you build is limited by the weakest link, so a Cat6A jack only yields a Cat6A channel with Cat6A cable.
| Category | Qualified bandwidth | Typical speed served | Standard |
|---|---|---|---|
| Cat5e | 100 MHz | 1000BASE-T (Gigabit) | ANSI/TIA-568 |
| Cat6 | 250 MHz | 1G; 10G to ~55 m | ANSI/TIA-568 |
| Cat6A | 500 MHz | 10GBASE-T to 100 m | ANSI/TIA-568 |
| Cat8 | 2000 MHz | 25G/40GBASE-T to ~30 m | ANSI/TIA-568 |
The PoE current rating is the most misread line. Under Power over Ethernet the same contacts carry data and DC power, so the jack must be rated for the current, not just the speed. VOOHU exposes discrete steps from 350 mA up to 1.5 A per contact; for IEEE 802.3bt (PoE++, up to 90 W across all four pairs) pick an integrated magjack rated for roughly ≥1 A per pair and check the terminal temperature rise. On an integrated magjack, also read the isolation (Hi-Pot ≥1500 V rms) — the transformer's primary-to-secondary barrier — which is a different figure from the connector's own dielectric withstanding voltage (1000 V AC). Finally, contact resistance (≤20 mΩ) and insulation resistance (≥500 MΩ) are the quiet quality lines; they, together with gold plating thickness, predict how the contact holds up over its ≥750-cycle life.
VOOHU Electronics manufactures RJ45 jacks / female modular sockets (母座) — not plugs or patch cables — spanning standard RJ45, low-profile (low-height), offset and combination jacks, plus integrated-magnetics (magjack) sink-type modules in 1×1, 1×N and 2×N layouts with 90° and 180° vertical mounting. The integrated range covers 100M, 1000M, 2.5G, 5G, 10G and HDBaseT, with or without LEDs, in commercial (0–70 °C) and industrial (−40 to +85 °C, up to −40 to +105 °C) grades, and PoE current options from 350 mA to 1.5 A per contact. Catalog examples include the single-port integrated magjack SYT111B372EA2A1DFL, the multi-port module SYT211T004AE4A7CBST6359, the shielded LED discrete jack WH59G82606623C12, the basic discrete base WH52B388121101, and the sink-type low-back part WH56I338821121101. Because every one of these lines is exposed as a selectable datasheet attribute, VOOHU can match — or custom-tool — a jack to a specific footprint, mount, plating tier or temperature grade. Discrete designs pair with VOOHU network transformers such as the single-port WHSG24301JM or dual-port WHDG48201P1 (isolation from 1500 V rms).
Read eight lines first: data rate / category (10/100M up to 10GBASE-T), whether the magnetics are integrated (magjack) or discrete, PoE current rating per contact (up to 1.5 A), mount (through-hole DIP or SMT), tab orientation (up or down), shielding (UTP or STP), operating temperature (commercial 0 to +70 °C vs industrial −40 to +85/+105 °C), and durability (≥750 mating cycles per IEC 60603-7). Together they fix the port's speed, power, board fit and field life; the remaining electrical lines confirm quality.
It is the maximum continuous DC current each contact can carry without overheating, because under Power over Ethernet the same pins carry both data and power. VOOHU lists jack options from 350 mA up to 1.5 A per contact. For IEEE 802.3bt (PoE++, up to 90 W across all four pairs) choose an integrated magjack rated for at least about 1 A per pair and verify the terminal temperature rise. Data rate and PoE current are independent lines, so a Gigabit jack can be non-PoE or rated to 1.5 A.
Dielectric withstanding voltage (DWV), commonly 1000 V AC for one minute on IEC 60603-7-class datasheets, tests the connector's own insulation between contacts and shell. A magjack's isolation voltage (Hi-Pot, ≥1500 V rms per IEEE 802.3) tests the built-in transformer's primary-to-secondary barrier. A discrete RJ45 jack lists only DWV; an integrated-magnetics jack lists both, so do not confuse the two figures.
Both the jack and the cable carry a category rating, and the channel is limited by the weaker of the two. The jack datasheet states the component category it was qualified to under ANSI/TIA-568 by meeting the connector NEXT and return-loss limits: Cat5e to 100 MHz, Cat6 to 250 MHz and Cat6A to 500 MHz. Pair a Cat6A jack with Cat6A cable to actually obtain a Cat6A channel.