A method and apparatus for measuring pressures in a gas turbine engine comprising a stator, a hollow rotatable shaft carrying a rotor and a first sensor having a plurality of inputs for pressure measured at respective test points on the rotor. Within the shaft are the following: a selector switch for selection of signals from respective test points, a stepping motor for driving the selector switch stepwise, a pressure module for converting the pressure signal from the sensor to an electrical signal, a further module for receiving inputs related to further conditions such as temperature, a first transmitter module for the telemetric remote transmission of the pressure signals from the pressure module, a second transmitter module for the telemetric remote transmission of the further conditions, a carrier for the first and second transmitter modules and a transmitter antenna connected to the first and second transmitter modules for transmitting the signals indicative of pressure and the further conditions as test data to the stator. A non-contact inductive current supply is connected to the first and second transmitter modules.