RJ12 6P6C (RS232) to USB Cable
RJ12 6P6C to USB serial cable is commonly used for equipment that communicates through RS232 but uses a compact RJ12 modular connector instead of a traditional DB9 connector. This cable is useful for PLC programming, HMI communication, industrial serial equipment, UPS/PDU console access, serial adaptors, and customised machinery control interfaces.
One Connector, Many Possible Pinouts
RJ12 6P6C describes the physical connector only. The RS232 signal assignment is not universal. Different brands and equipment families may use different pin assignments for TXD, RXD, GND, RTS, CTS, DCD, DTR, or even +5V power.
For this reason, the cable should always be selected or manufactured according to the equipment model, user manual, or confirmed pinout table.
Typical RJ12 6P6C RS232 to USB Serial Pinout
This is one common wiring example for an RJ12 6P6C RS232 interface connected to a USB serial converter circuit.
| RJ12 Pin | RJ12 Signal | USB Serial Chip Signal | Connection Type |
|---|---|---|---|
| 1 | TXD | RXD | Transmit data to USB serial receiver |
| 2 | CTS | RTS | Hardware flow control |
| 3 | GND | GND | Signal ground |
| 4 | GND | GND | Signal ground |
| 5 | RXD | TXD | Receive data from USB serial transmitter |
| 6 | RTS | CTS | Hardware flow control |
Important: USB wires are not directly connected to RJ12 RS232 pins. A USB-to-serial converter chip is required inside the cable or adapter housing.
Application Examples
Different machines and control systems may use different RJ12 RS232 pinouts. Below are example application-style diagrams showing how the cable may be customised for specific equipment families.
DirectLOGIC / CLICK PLC Cable
Used for PLC programming and serial communication on compatible PLC RJ12 ports. Common applications include industrial control panels, machine automation, and field maintenance.
C-more Micro HMI Cable
Used for HMI programming, project transfer, and communication between a PC and a compatible micro-graphic operator interface panel.
PLC Programming Cable
Suitable for selected PLC systems that use RJ12 6P6C as the RS232 communication port. Pinout must match the exact PLC model and port number.
Multi-Port Serial Adaptor Cable
Used where compact RJ12 sockets are fitted to multi-port RS232 adaptor cards or serial expansion equipment. These applications may require additional handshake signals such as DCD, DTR/RTS, and CTS.
Where RJ12 RS232 to USB Cables Are Commonly Used
PLC Programming
Used to connect a PC to PLC programming ports for configuration, monitoring, downloading, and troubleshooting.
HMI & Operator Panel
Used for project transfer, parameter setup, and communication with compact operator interface panels.
Industrial Serial Devices
Used on controllers, data terminals, scales, analyzers, label machines, and other RS232 equipment with modular ports.
Before Ordering a Custom RJ12 to USB Serial Cable
- Confirm the equipment brand and model number.
- Check whether the port is RS232, TTL UART, RS485, or another serial standard.
- Confirm the RJ12 pin numbering direction from the equipment manual.
- Identify whether hardware flow control is required.
- Confirm whether any pin supplies +5V power and whether it should be connected.
- Provide the required cable length and connector orientation.
A wrong RS232 pinout may prevent communication and, in some cases, may damage the connected equipment if power pins are incorrectly connected.
Need a Custom RJ12 6P6C RS232 to USB Cable?
We can help manufacture RJ12 6P6C to USB serial cables according to your equipment pinout, cable length, and application requirement.
