Electronic pulse filtering system

Claim 2

A pulse filtering system adapted to pass to an output circuit only those pulses of a train of substantially uniformly spaced input pulses whose repetition frequency exceeds a predetermined frequency, said system comprising, a normally closed gating circuit, a bi-stable circuit having first and second output terminals operative in response to a train of input pulses to produce outward pulses alternately at said first and second output terminals, means for applying a train of input pulses in parallel to said gating circuit and to said bi-stable circuit, first and second single-shot multivibrators arranged to be switched by the pulses from the first and second output terminal respectively of said bi-stable circuit, said single-shot multivibrators each being operative to produce trains of rectangular output pulses of substantially equal durations equal to the repetition period at said predetermined pulse repetition frequency, means for adding the pulses from said first and second single-shot multivibrators and operative to produce a direct current signal only when the pulse repetition frequency of said input pulses exceeds said predetermined frequency, and means for coupling said direct current signal to said gating circuit to open the same and allow the transmission of said input pulses therethrough.

Claim 3

A pulse filtering circuit adapted to pass to an output circuit only those pulses of a train of substantially uniformly spaced input pulses whose frequency differs from a predetermined repetition frequency, said circuit comprising, a gating circuit, a control circuit having input and output terminals, and means for applying said train of input pulses to said gating circuit and to the input terminal of said control circuit in parallel, said control circuit including means operative in response to said input pulses to generate two like trains of rectangular pulses each of a repetition frequency equal to one-half that of the repetition frequency of said input pulses and displaced relative to each other by the period of said input pulses, the duration of the rectangular pulses in each train being equal to the repetition period at said predetermined repetition frequency, means for adding the pulses in said two like trains and operative to produce a direct current control signal at said output terminal only when the period of said input pulses is shorter than the duration of said rectangular pulses, and means for coupling said control signal from said output terminal to said gating circuit.

Claim 4

A pulse filtering circuit adapted to pass to an output circuit only those pulses of a train of substantially uniformly spaced input pulses whose frequency differs from a predetermined repetition frequency, said circuit comprising, a gating circuit, a control circuit having input and output terminals, and means for applying said train of input pulses to said gating circuit and to the input terminal of said control circuit in parallel, said control circuit including means operative in response to said input pulses to generate two like trains of rectangular pulses each of a repetition frequency equal to one-half that of the repetition frequency of said input pulses and displaced relative to each other by the period of said input pulses, the duration of the rectangular pulses in each train being equal to the repetition period at said predetermined repetition frequency, means for adding the pulses in said two like trains and operative to produce a direct current control signal at said output terminal only when the period of said input pulses is shorter than the duration of said rectangular pulses, and means for coupling said control signal from said output terminal to said gating circuit.

Claim 5

A pulse filteriing circuit adapted to pass to an output circuit only those pulses of a train of substantially uniformly spaced input pulses whose repetition frequency is below a predetermined repetition frequency, said circuit comprising, in combination, a normally open gating circuit biased to be closed upon application thereof of a control signal in excess of a predetermined magnitude, a control circuit having input and output terminals, means for applying said train of input pulses in parallel to said gating circuit and to the input terminal of said control circuit, said control circuit including means operative in response to said input pulses to generate two trains of rectangular pulses each having a repetition frequency equal to one-half the repetition frequency of said input pulses and displaced relative to each other by the spacing between said input pulses, the duration of the rectangular pulses in each train being equal to the repetition period at said predetermined repetition frequency, means for adding the pulses in said two trains of rectangular pulses and operative to produce at said output terminal a direct current control signal in excess of said predetermined magnitude only when the repetition period of said input pulses is shorter than the duration of said rectangular pulses, and means for coupling said control signal to said gating circuit to close said gating circuit, whereby only those pulses having a repetition frequency less than said predetermined frequency are passed to an output circuit.

Claim 6

A pulse filteriing circuit adapted to pass to an output circuit only those pulses of a train of substantially uniformly spaced input pulses whose repetition frequency is below a predetermined repetition frequency, said circuit comprising, in combination, a normally open gating circuit biased to be closed upon application thereof of a control signal in excess of a predetermined magnitude, a control circuit having input and output terminals, means for applying said train of input pulses in parallel to said gating circuit and to the input terminal of said control circuit, said control circuit including means operative in response to said input pulses to generate two trains of rectangular pulses each having a repetition frequency equal to one-half the repetition frequency of said input pulses and displaced relative to each other by the spacing between said input pulses, the duration of the rectangular pulses in each train being equal to the repetition period at said predetermined repetition frequency, means for adding the pulses in said two trains of rectangular pulses and operative to produce at said output terminal a direct current control signal in excess of said predetermined magnitude only when the repetition period of said input pulses is shorter than the duration of said rectangular pulses, and means for coupling said control signal to said gating circuit to close said gating circuit, whereby only those pulses having a repetition frequency less than said predetermined frequency are passed to an output circuit.