RJ50 vs RJ45: One Extra Pair, Different World
Quick answer / TL;DR: Short answer: RJ50 has ten contacts and is used for serial and industrial signalling, not Ethernet. An RJ50 plug will not seat correctly in an RJ45 socket, and forcing it damages the contacts. Identify the port by contact count before ordering, and never assume an RJ45-shaped port is Ethernet.
Same rack unit, two densities: 48 ports doubles the terminations behind one panel.RJ45 is an eight-position, eight-contact connector used for Ethernet. RJ50 is ten-position, ten-contact and appears in industrial controls, serial links and some instrumentation.
They look similar and do not interchange.
Side by Side
| Property | RJ45 | RJ50 |
|---|
| Positions | 8 | 10 |
| Contacts | 8 | 10 |
| Typical use | Ethernet | Serial, industrial |
| Cable | Cat5e and up | Often flat or shielded |
| Standard | TIA-568 | Vendor specific |
The extra pair makes RJ50 wider, so it neither latches nor makes reliable contact in an eight-position socket.
Where You Meet It
- Industrial controllers with serial consoles
- Point of sale equipment
- Lab instruments
- Legacy telecom equipment
- Custom cable assemblies
In these applications the pinout is vendor specific, so the cable must be built to the equipment manual rather than to a category standard.
Real-World Applications
A technician connecting to an industrial controller console needs an RJ50 to DB9 cable built to that vendor's pinout. Using an Ethernet patch lead, even if it fits, will not work and may damage the port.
Standards and Verification
| Reference | Relevance |
|---|
| TIA-568.2-D | RJ45 and Ethernet |
| IEC 60603-7 | 8-way connector interface |
| Vendor manuals | RJ50 pinouts |
Pinout for a specific RJ50 device is not provided in the knowledge base. Check the equipment manual.
Practical Notes
Count the contacts in the plug before inserting anything. The difference is visible and decisive.
Related reading: ethernet cable — blogs/news/ethernet-cable
Related reading: rj45 vs ethernet — blogs/news/rj45-vs-ethernet
Related reading: rj12 vs rj45 — blogs/news/rj12-vs-rj45
Frequently Asked Questions
Is RJ50 Ethernet?
No. It is used for serial and industrial links.
Will an RJ45 cable fit?
It may enter, but it will not work reliably.
Where do I get the pinout?
From the equipment manual, not from a cabling standard.
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