You may need more than just a pin-to-a-pin connection. All MOH devices I know of have RCA or 3.5 mm jack OUTPUTS, which normally corresponds to the phone system's 600 Ohm RCA INPUT. If you have a RJ11(or RJ45) INPUT, you may at the very least require a conversion between the different impedances or a specialized device. For example, Lucent (now Avaya) Merlin and Merlin Legend phone systems require a device (model KS-23395L3) to convert a 600 Ohm RCA into the system's RJ45 port. Depending on your system, you may need such device as well.
Dmitri Abaimov, RCDD