With an RJ45 cable end what is the difference between a keyed end and a regular end?

The primary difference between a keyed RJ45 and a regular (non-keyed) RJ45 connector is a physical design feature intended to prevent "incorrect plugging"—a concept known as mechanical keying.

While both connectors look almost identical at a glance, they serve different operational purposes.

1. Physical Design

• Regular RJ45: This is the standard 8P8C (8 position, 8 contact) connector used for almost all Ethernet networking. It has a rectangular body with a flexible locking tab on the bottom center. It is designed to fit into any standard RJ45 port.

• Keyed RJ45: This connector features a small, raised moulded ridge (the "key") on one side of the connector body. This ridge prevents the plug from being inserted into a standard, non-keyed socket.

2. The Functional Purpose

The key exists to ensure that a specific cable is only plugged into a specific, matching jack. This is crucial in environments where multiple types of signals are running through the same patch panel or wall outlet.

• Signal Protection: In older or specialised telecommunications systems, some RJ45 ports might carry high-voltage DC power or different data protocols that could damage a standard network card.

• Identification: It acts as a physical "fail-safe" so that a user cannot accidentally plug a data-sensitive or high-voltage line into a standard laptop or switch.

3. Compatibility

• Regular Plugs: These can technically fit into a keyed jack, but they will not lock properly or may have a loose connection because the jack is expecting that extra slot for the key.

• Keyed Plugs: These cannot be inserted into a standard Ethernet port. If you try to force it, you will likely snap the plastic or damage the internal pins of the socket.