SDL 4P Male Plug, Shielded 50 Ohm Pin & Earth Modular Terminal Connector, Tray Pack

Shielded 4P SDL Male Plug with Pin and Earth, 50 Ohm Tray Pack

This RJ9 SDL modular terminal plug is a 4-position male connector built as a Shielded Data Link (SDL) cable plug, not as a telephone handset crystal head. Buyers who search “RJ9 4P” usually mean the compact four-position modular nose. What they need on an industrial or instrument harness is the SDL version: a keyed housing, dual side latches, a metal shield, and a dedicated earth path that bonds the cable braid to the receptacle shell. This part is that plug — 4P pin plus earth, 50-ohm shielded class, shipped in trays for OEM and EMS lines.

SDL was introduced so a modular-looking plug could carry shielded data without the crosstalk and ground bounce of an unshielded 4P4C. The 50-series geometry (1.27 mm centerline) is the interface still used on industrial I/O, printers, POS, medical peripherals, test fixtures, and many PLC or operator-panel tails. If your BOM calls an AMP / TE 4-position SDL plug assembly, a 4P shielded pin-and-earth terminal, or a tray-packed 50-ohm modular plug, this is the correct family. For Ethernet or VFD keypad work, do not use this SKU — see our RJ45 8P8C modular plugs instead.

A electrical connector in this class has two jobs: eight-or-fewer signal blades must wipe cleanly, and the shield must present a low-impedance path to chassis so electromagnetic interference does not ride the cable into the board. The 50-ohm designation on this plug matches the 50-series SDL system and the 50 Ω characteristic impedance common on shielded instrument and RF-adjacent data leads. Confirm cable impedance and receptacle series (36 or 50) before you freeze the harness drawing.

Pin Contacts, Earth Path, and Why Shielding Matters

Four gold-plated copper-alloy pins carry the circuit. A separate earth member ties the tin-plated shield can to the cable braid or drain. That is the “pin & earth” construction procurement writes on the PO. Without the earth member, the metal shell is only cosmetic and the cable fails EMC at the first meter. With it, the plug and the board receptacle form a continuous Faraday path from jacket to PCB ground pad.

The housing is glass-filled polycarbonate, typically smoke gray or clear-gray, UL 94 V-2. The shield is brass or carbon steel with bright tin. Contacts are selective gold, 50 microinches (1.27 µm) over nickel as standard — the thickness industrial buyers specify when the plug will be mated hundreds of times on a service cable. Current class is 1.5 A per contact at 30 V. Operating range is −20 °C to +80 °C. Termination is crimp / IDC for 24–26 AWG (0.12–0.21 mm²) with conductor insulation about 1.14–1.27 mm. Round jacketed shielded cable is the usual mate; flat shielded ribbon is available on the same 4P SDL nose.

Not a telephone RJ9 — do not crimp it as 4P4C

A consumer RJ9 / RJ10 / RJ22 handset plug is an unshielded 4P4C crystal head with a single top latch. An SDL 4P plug is keyed, uses side latches, and will not seat correctly in a telephone jack — and a telephone plug will not latch in an SDL receptacle. Mixing them is the most common incoming-quality failure on mixed-connector lines. Keep this part on the SDL / shielded-data bin, next to the matching 4P SDL board receptacles and shielded 4-conductor data cable.

Where this 4P shielded plug is used

Typical assemblies: cable-to-board tails on industrial controllers, shielded sensor and encoder pigtails that use a 4P modular face, POS and printer I/O, medical cart peripherals, ATE fixtures, and replacement leads for AMP 50-series SDL ports. EMS plants specify tray pack so the plug can be counted, kitted, and presented to a bench crimp press without a polybag dump. Service depots order the same tray as a spare so field techs do not substitute a telephone crystal head.

Need the other end of the link? Add a shielded 4P SDL PCB receptacle or a finished SDL cable assembly on the same order.

Technical Specifications

Send cable OD, braid style (foil + drain or braid), and the receptacle part number to our engineering desk before a first production lot. We will confirm earth-tab geometry and return a crimped sample in the same tray you will receive in volume.

How OEM and EMS Buyers Should Write the PO

Specify: SDL 4P male plug, shielded, pin and earth, 50-ohm / 50-series, tray packaging. Add wire AWG, round or flat cable, and gold thickness. Do not write “RJ9 4P4C telephone plug” or the line will ship the wrong latch. Tray pack is the default for SMT and harness cells; bag pack is only for MRO spares if you ask for it.

Incoming inspection

Check four signal blades plus a continuous shield/earth member. Confirm side latches, not a single top tab. Confirm the plug keys into your SDL receptacle and will not enter a telephone jack. Continuity: pins 1–4 isolated from the shell; shell bonded to the drain after crimp. Gold should be 50 µin class unless you ordered flash gold for a one-time mate. Count pieces by tray pocket, not by bag weight.

Frequently Asked Questions

Is this a standard RJ9 telephone plug?

No. It uses a 4-position modular outline, which is why catalogs still say RJ9 SDL, but the latch, keying, shield, and earth contact are SDL. It will not reliably mate a handset jack. Use a 4P4C crystal head for telephony; use this plug for shielded data.

What does “pin & earth” mean?

Four pins are the circuit. Earth is the shield termination that bonds cable braid to the metal shell and then to the board receptacle ground. If you only need four signals and no EMC path, you do not need this SKU.

What does 50 ohm refer to?

It marks the 50-series SDL system and the 50 Ω impedance class used on many shielded instrument cables. It is not a 75 Ω video plug and not an unshielded telephone plug. Match the cable impedance and the 50-series receptacle. 36-series SDL parts are a different mechanical family.

Will it fit TE / AMP 4-520424 or 4-1761184 receptacles?

It is tooled as a 50-series 4-position SDL male plug in that interface family. Always do a first-article mate on your exact receptacle (top-entry vs side-entry, keyed vs standard). We do not print TE or AMP marks unless you order a licensed OEM part.

What cable and tool do we need?

Use 24–26 AWG shielded cable, fold the braid onto the earth tab, and crimp with an SDL / AMP-style die — not a generic RJ11/RJ45 telephone tool. Wrong dies crush the shield and open the earth path. We can supply a crimp spec and a sample lead.

Why tray packaging instead of a bag?

Trays keep the shield cans from nesting and scratching gold. They give a hard count for incoming IQC and sit on an EMS kit cart without static bags dumped on the bench. Tell us pockets per tray if you need a custom nest.

Can you private-label or change gold thickness?

Yes. Flash, 15 µin, or 50 µin gold, laser marks, and your part number on the tray label are standard OEM options. MOQ depends on the change. See SDL connectors for 6P and 8P mates in the same series.

Is the shield enough for a factory floor?

The plug provides a 360° shell and an earth bond. EMC still depends on braid coverage, drain termination length, and the board receptacle’s ground vias. For VFDs and motor leads, keep this signal cable away from power and use a ferrite if the cabinet is noisy. This plug is signal-only (1.5 A / 30 V).

Ready to quote? Send annual volume, cable drawing, receptacle PN, and whether you need loose tray plugs or finished SDL assemblies. We will return a sample tray and tiered pricing.