Abstract: A system for transmitting an EPR (Engine Pressure Ratio) from a gas turbine is provided with a resolver component (30) which modifies the EPR in accordance with variations in the optimum EPR for a particular turbine under particular conditions. The information from an EPR gauge is transmitted by a synchro transmitter, and is received by a differential transmitter (31) associated with the particular engine being monitored. The differential transmitter (31) is adjusted in accordance with pressure (at 33) and temperature (at 56) conditions in order to provide an EPR reading which is compensated in accordance with actual conditions of pressure and temperature. The differential transmitter (31) is also adjusted (at 45) in order to provide an output which is further varied in accordance with a variation in the optimum EPR under standard conditions for the particular turbine associated with the differential transmitter.