Crystal oscillator having plural, selectable feedback paths and adjustable frequencydetuning means

Claim 1

IN APPARATUS FOR MEASURING DISTANCE BY TRANSMITTING ELECTROMAGNETIC WAVES OF DIFFERENT FREQUENCIES FROM RESPECTIVE OPPOSITE ENDS OF A DISTANCE TO BE MEASURED, WITH THE FREQUENCY DIFFERENCE BETWEEN THE TRANSMITTED WAVES BEING IN THE AUDIO RANGE, TO OBTAIN A ROUGH MEASUREMENT, AND TRANSMITTING A SECOND SERIES OF ELECTROMAGNETIC WAVES OF DIFFERENT AND HIGHER FREQUENCIES BUT HAVING THE SAME FREQUENCY DIFFERENCE IN THE AUDIO RANGE, TO OBTAIN A FINE MEASUREMENT, AND USING A MAIN TRANSMITTER-RECEIVER UNIT AT ONE END OF THE DISTANCE TO BE MEASURED AND AN AUXILIARY TRANSMITTER-RECEIVER UNIT AT THE OTHER END OF SUCH DISTANC: THE IMPROVEMENT COMPRISING A SINGLE SIGNAL GENERATOR USABLE IN EITHER OF SAID UNITS; AND SIGNAL GENERATOR INCLUDING A PAIR OF PIEZO-ELECTRIC RESONATORS HAVING SUBSTANTIALLY THE SAME RESONANCE FREQUENCY; THE PAIR OF RESONATORS IN SAID SIGNAL GENERATOR BEING INCLUDED IN AN OSCILLATOR CIRCUIT FURTHER INCLUDING A PAIR OF FEEDBACK CIRCUITS EACH CONNECTED WITH A RESPECTIVE RESONATOR AND EACH FEEDBACK CIRCUIT INCLUDING RESPECTIVE FREQUENCY-ADJUSTING MEANS FOR THE ASSOCIATED RESONATOR; THE TWO FEEDBACK CIRCUIT OF SAID OSCILLATOR BEING TUNED TO SLIGHTLY DIFFERENT FREQUENCIES; SAID OSCILLATOR CIRCUIT FURTHER INCLUDING ADJUSTABLE FREQUENCY DETUNING CIRCUIT MEANS; A SIGNAL OUTPUT TERMINAL A BUFFER AMPLIFIER COUPLED BETWEEN SAID OUTPUT TERMINAL AND SAID FEEDBACK CIRCUIT; SAID OSCILLATOR INCLUDING A FIRST, NEGATIVE POTENTIAL SOURCE, A FIRST SWITCH MEANS CONNECTED TO SAID FIRST NEGATIVE POTENTIAL SOURCE AND TO SAID FEEDBACK CIRCUITS AND SELECTIVELY OPERABLE TO CONNECT EITHER ONE OF SAID FEEDBACK CIRCUITS TO SAID FIRST NEGATIVE POTENTIAL SOURCE, A SECOND POTENTIAL SOURCE HAVING A POSITIVE TERMINAL CONNECTED TO SAID FEEDBACK CIRCUITS, AND A THIRD POTENTIAL SOURCE HAVING A NEGATIVE TERMINAL; AND SECOND SWITCH MEANS CONNECTED TO THE POSITIVE TERMINAL OF SAID SECOND POTENTIAL SOURCE, THE NEGATIVE TERMINAL TO SAID THIRD POTENTIAL SOURCE AND IN COMMON TO SAID DETUNING CIRCUIT MEANS AND SAID RESANOTORS, AND SELECTIVELY OPERABLE TO CONNECT SAID DETUNING CIRCUIT MEANS AND SAID RESONATORS TO EITHER THE POSITIVE TERMINAL OF SAID SECOND POTENTIAL SOURCE OR THE NAGATIVE TERMINAL OF SAID THIRD POTENTIAL SOURCE, TO SELECTIVELY DETUNE SAID OSCILLATOR.