Compass display circuit

Claim 1

For use with a digital magnetic compass providing a serial pulse train representative of compass heading, display circuitry for converting received serial pulses to a parallel form for driving output indicators for selective numerical display of compass heading and elapsed time, said circuitry comprising: a clock source providing clock pulses at a predetermined frequency; a divider circuit operative in response to said clock pulses for providing a plurality of timing pulse trains of respective different frequencies; means for receiving said serial pulses from a digital magnetic compass; envelope detector means operative to provide a gating signal of a duration corresponding to the duration of said received serial pulses; counter means operative in response to said received serial pulses and said gating signal to provide parallel output signals representative of magnetic compass heading; selector means operative to select one of said timing pulse trains; a dimmer circuit operative in response to one of said timing pulse trains to provide output signals of selectable pulse width and coupled to said counter means for control of the blanking rate thereof; synchronizing means coupled to said counter means and operative in response to one of said timing pulse trains to synchronize processing of said received serial pulses and timing pulse trains; means coupled to said selector means and to said envelope detector means for inhibiting signal processing in the presence of contact bounce noise; means operative in response to one of said timing pulse trains for providing said selected pulse train to said counter means to the exclusion of said received serial pulses to cause provision by said counter means of parallel output signals representative of elapsed time; and display means operative in response to said parallel output signals for providing a numerical indication of compass heading or elapsed time.