A digital interface sensing apparatus includes a sensor, an analog detecting circuit, an analog to digital (A/D) converter, a signal cable, and an interface switch circuit. The sensor senses an external analog signal. The analog detecting circuit detects the sensed analog signal from the sensor. The A/D converter converts the sensed analog signal to a digital signal and receives a clock signal and a data demand signal. The A/D converter sends the digital signal in response to the A/D converter receiving the clock signal and the data demand signal. The interface switch circuit includes a multiplexer and a recommended standard 422 (RS-422) transceiver. The RS-422 transceiver is connected between the A/D converter and the multiplexer to switch RS-422 digital signal and transistor-transistor logic (TTL) signal. The multiplexer is connected between the A/D converter and the signal cable to selectively transfer RS-233 and RS-422 signals.