Frequency detection system

Claim 2

A frequency detection system including in combination: a. frequency-to-voltage conversion means comprising differentiating means for providing spiked output pulses in response to a rectangular wave input signal, a one-shot multivibrator coupled to receive spiked pulses of a selected polarity from said differentiating means to thereby provide an output signal having an average DC voltage proportional to the frequency of the input signal, and means for under filtering said average DC voltage at the output at said one-shot multivibrator for providing a DC ripple voltage for driving voltage responsive means, and b. voltage responsive means coupled to said filtering means and being responsive to said DC ripple voltage to provide an output signal which is either at one or the other of two DC voltage levels or is alternating between said two voltage levels.

Claim 3

The frequency detection system defined in claim 1 wherein said voltage responsive means includes a Schmitt trigger having a preselected hysteresis voltage range and responsive to said DC ripple voltage having values above and below said hysteresis voltage range to provide an alternating output signal, said Schmitt trigger also providing a first DC output voltage when said ripple voltage is below a maximum value of hysteresis voltage of said Schmitt trigger and providing a second DC outPut voltage when said ripple voltage is above a minimum value of hysteresis voltage of said Schmitt trigger.

Claim 4

The frequency detection system defined in claim 1 wherein said voltage responsive means includes output circuit means responsive to said alternating output signal to remain fully conductive as long as said alternating output signal is present, said output circuit means being nonresponsive to a DC voltage applied thereto.

Claim 5

A frequency detection system including in combination: a. means for receiving a fixed frequency input signal, b. frequency-to-voltage conversion means coupled to said receiving means for providing an output DC ripple voltage, the level of which is proportional to the frequency of the input signal comprising, wave shaping means connected to receive said fixed frequency input signal to provide an output voltage having a fixed duty cycle, differentiating means connected to said wave shaping means for providing spiked output pulses, a one-shot multivibrator connected to receive said spiked output pulses of a selected polarity for providing output pulses having an average voltage which is proportional to the frequency of said fixed frequency input signal, and filter means connected to said one-shot multivibrator for providing an under filtered DC ripple voltage for driving said voltage responsive means, and c. voltage responsive means connected to receive said DC ripple voltage and responsive to said DC ripple voltage to provide a voltage at either one or the other of two fixed levels or an alternating output voltage, said voltage responsive means including output circuit means responsive to said alternating output voltage to remain fully conductive as long as said alternating output signal is present, and said output circuit means being nonresponsive to a DC voltage applied thereto.

Claim 6

A frequency detection system including in combination: a. means for receiving a fixed frequency input signal, b. frequency-to-voltage conversion means coupled to said receiving means for providing an output DC ripple voltage, the level of which is proportional to the frequency of the input signal comprising, wave shaping means connected to receive said fixed frequency input signal to provide an output voltage having a fixed duty cycle, differentiating means connected to said wave shaping means for providing spiked output pulses, a one-shot multivibrator connected to receive said spiked output pulses of a selected polarity for providing output pulses having an average voltage which is proportional to the frequency of said fixed frequency input signal, and filter means connected to said one-shot multivibrator for providing an under filtered DC ripple voltage for driving said voltage responsive means, and c. voltage responsive means connected to receive said DC ripple voltage and responsive to said DC ripple voltage to provide a voltage at either one or the other of two fixed levels or an alternating output voltage, said voltage responsive means including output circuit means responsive to said alternating output voltage to remain fully conductive as long as said alternating output signal is present, and said output circuit means being nonresponsive to a DC voltage applied thereto.

Claim 7

The frequency detection system defined in claim 4 wherein said voltage responsive means include a Schmitt trigger having a hysteresis voltage VH which is the voltage range between the level required to turn on said trigger and the level required to turn on said Schmitt trigger and the level at the Schmitt trigger turns off, said Schmitt trigger being responsive to different envelopes of DC ripple voltage applied thereto to provide three different outputs indicative of the frequency of the fixed frequency signal.

Claim 8

The frequency detection system defined in claim 5 wherein said wave shaping means include a squaring circuit connected to receive a sine wave input signal and responsive to said sine wave signal to provide a rectangular wave output voltage for driving said frequency-to-voltage conversion means.

Claim 9

The frequency detection system defined in claim 6 which further includes output circuit means connected to the output of said Schmitt trigger, said output circuit means having a blocking capacitor therein which renders said output circuit means nonresponsive to a DC voltage at the output of said Schmitt trigger and operative to couple to an AC voltage to an output transistor to turn on said output transistor and maintain said output transistor conducting during the presence of an AC voltage at the output of said Schmitt trigger.