I had picked up a Baytech MP power strip recently, and wanted to monitor it with MRTG.
For $1, I got a Cisco DE9-RJ45 cable (blue). Because I’m lazy, I just cut it halfway and connected the relevant wires.
Pin mapping:
| RJ45 side | DE-9 side | Actual DE-9 pin | Signal |
| 2 | 4 | 5 | Ground |
| 4 | 3 | 2 | TXD (Device to Host) |
| 5 | 6 | 3 | RXD (Host to Device) |
Connection seems to be 9600 Baud, N-8-1.
I got a command prompt, and you can enter “status” to view the current data, with output like this:
Average Power: 107 Watts
True RMS Voltage: 120.7 Volts
True RMS Current: 1.2 Amps
Maximum Detected: 2.1 Amps
This can be easily retrieved and split for logging with MRTG or any other app.