Abstract: A digital test system for generating a test signal in the form of an amplitude and/or phase modulated sinusoidal signal at a given carrier frequency is disclosed. Arbitrary amplitude and phase modulation functions may be selected and are provided to the system in the form of digitally encoded data streams. The system does not require a digital multiplier. A signal in the form of an unmodulated carrier signal may also be generated.

Abstract: Method and apparatus are provided for measuring the settling time, relative to a reference time, of an analog signal having a varying amplitude. The apparatus includes a pair of comparators U1 and U2 for comparing the amplitude of the analog signal with first and second reference signals V.sub.Ref 1 and V.sub.Ref 2. The comparators U1 and U2 are connected to edge detector 22 which supplies a reset signal to a second counter 26 whenever the amplitude of the analog signal is not between the first and second reference signals. Oscillator 32 drives counters 25 and 26 which count pulses from oscillator beginning at the reference time and continuing until the second counter 26 contains a predetermined count. Because the second counter 26 is reset by the edge detector 22 whenever the analog waveform exceeds either of the reference signals, the difference between counter 25 and counter 26 at any subsequent time after the waveform has settled will be the settling time of the analog waveform.