The NTE974 consists of two digital phase detectors, a charge pump, and an amplifier. In combination with a voltage controlled multivibrator, it is useful in a broad range of phaselocked loop applications. The circuit accepts MTTL waveforms at the R and V inputs and generates an error voltage that is proportional to the frequency and/or phase difference of the input signals. Phase detector #1 is intended for use in systems requiring zero frequency and phase difference at lock. Phase detector #2 is used if quadrature lock is desired. Phase detector #2 can also be used to indicate that the main loop, utilizing phase detector #1, is out of lock. Absolute Maximum Ratings: