Circuitry in a scanning receiver for speeding up the generation of a reception or non-reception criterion

Circuitry in a wireless signal receiver for generating a receive criterion, i.e. for detecting the reception or non-reception of a signal, for receivers being alternating on reception on several channels and having facilities for seeking a free or an occupied channel, of the type having first circuit means for generating a DC signal as a noise criterion proportional to the strength of the noise at the receiver output, for generating a criterion for the reception or the non-reception of a wireless signal if the value of said noise criterion is below or above a certain limit potential, further having second circuit means dividing the time into measurement periods, a capacitance with a first and a second terminal, the first terminal being connected with any fixed potential, third circuit means, controlled by said second circuit means, for connecting said second terminal of said capacitance, before the beginning of a measurement period, to a base, potential having one of the possible extreme values of the noise criterion, and during the measurement period via a resistance to the potential of the noise criterion, the improvement comprising:

• fourth circuit means, including a digital output, for comparing the potential at said second terminal with a threshold potential having a value between said base potential and said limit potential, the potential appearing at said digital output depending solely upon the polarity of the difference between the potentials to be compared, fifth circuit means with an input, connected to the output of the fourth circuit means determining the reception or non-reception of a signal based upon the moment at which a change of the potential at its input occurs within the respective one of said measuring periods.