We’re using an MTCBA-E-U and we want to input the voice signal from the modem to the PC (so that we can monitor DTMF signals). To do this, we need the pinout of the RJ10 handset connector.

The RJ-10 is pinned

1 2 3 4
I I I I

Pin1 MIC +
Pin2 SPKR +
Pin3 SPKR -
Pin4 MIC -