A zero-heat-flux, deep tissue temperature measurement system measures internal body temperature by way of a probe having a heater and thermal sensors arranged in a zero-heat-flux construction. The measurement system includes control mechanization that determines heater and skin temperatures based upon data obtained from the probe and uses those temperatures to calculate a deep tissue temperature. The measurement system includes a signal interface cable having a connector where a probe can be releasably connected to the system. The cable and attached connector are a removable and replaceable part of the system, separate from the probe. The measurement system provides an output signal imitating a standard input signal configuration used by other equipment.