The T2-135 is a Tracker2 that installs in an Alinco DR-135T or similar radio. The radio must be in "data" mode to access the TNC. The T2-135 is the same as an OT2m except it doesn't have a built in temperature sensor and doesn't support the VOLTAGE command or low voltage inhibit. SWDCD (software data carrier detect) is also forced ON for the T2-135. Only Port A is brought out to the DE-9 connector on the back of the radio. Port B is available for "input only" on the data connector on the front of the radio.