Tuning device for musical instruments

Claim 1

In a tuning device for musical instruments the input signals of which are a filtered tone oscillation, a digital oscillation signal, and a reference signal with an input means for the measurement of the number of periods or half-periods of a tone during a present reference time period including a microphone, an amplifier, a filter for the prevention of zero transits extraneous to the fundamental tone oscillation, a Schmitt-trigger for the conversion of the filtered tone frequency voltage into the digital oscillation signal, an AND-gate which is open during a preset reference time, a reference period generator, a reference signal counter, an oscillation counter a decoder and a display means, and a flip-flop for the generation of an oscillation period signal, which is set by a triggering circuit and reset by a resetting circuit and which supplies an enable signal by which the reference period generator is triggered and the two counter are enabled, the improvement in combination therewith for the triggering circuit comprising a rectifier the input of which is an amplitude of the filtered tone oscillation voltage, a first smoothing device, and a first Schmitt-trigger the output of which sets the flip-flop for the generation of an oscillation period signal, and for the resetting circuit fed by the zero transit signal comprising an inverter the input of which is the digital oscillation signal, a second smoothing device, and a second Schmitt-trigger the output of which resets said flip-flop.