Crystal controlled multivibrator

Claim 1

A FREE-RUNNING MULTIVIBRATOR CIRCUIT FOR PRODUCING A SUBSTANTIALLY SQUARE WAVE VOLTAGE OF STABLE FREQUENCY, COMPRISING FIRST AND SECOND TRANSISTORS EACH HAVING BASE, EMITTER AND COLLECTOR ELECTRODES, AND CIRCUIT MEANS COMPRISING: A RESISTOR CONNECTED BETWEEN EMITTER ELECTRODE OF THE FIRST TRANSISTOR AND A POINT OF FIXED REFERENCE POTENTIAL, MEANS FOR BIASING THE BASE ELECTRODE OF SAID FIRST TRANSISTOR INCLUDING A RESISTOR HAVING ONE END CONNECTED TO SAID POINT OF FIXED REFERENCE POTENTIAL, A PARALLEL RESONANT CIRCUIT CONNECTED BETWEEN THE OTHER END OF THE LASTMENTONED RESISTOR AND THE BASE ELECTRODE OF SAID FIRST TRANSISTOR, SAID RESONANT CIRCUIT BEING IN SERIES RELATION WITH SAID LAST-MENTIONED RESISTOR IN THE INPUT CIRCUIT OF SAID FIRST TRANSISTOR AND BEING TUNED TO THE SELECTED OPERATING FREQUENCY OF THE OSCILLATOR, MEANS COUPLING THE COLLECTOR ELECTRODE OF SAID FIRST TRANSISTOR TO THE BASE ELECTRODE OF SAID SECOND TRANSISTOR, A FEEDBACK CONNECTION INCLUDING A CRYSTAL BETWEEN THE COLLECTOR OF SAID SECOND TRANSISTOR AND THE BASE ELECTRODE OF SAID FIRST TRANSISTOR, SAID CRYSTAL BEING CUT TO SERIES RESONATE AT SAID SELECTED OPERATING FREQUENCY, SAID RESONANT CIRCUIT SERVING TO REDUCE THE ATTENUATION OF THE FEEDBACK SIGNAL IN THE INPUT CIRCUIT OF SAID FIRST TRANSISTOR, A RESISTOR CONNECTED BETWEEN THE EMITTER ELECTRODE OF SAID SECOND TRANSISTOR AND SAID POINT OF FIXED REFERENCE POTENTIAL, AND MEANS FOR DERIVING THE SQUARE WAVE OUTPUT VOLTAGE FROM ACROSS THE LATTER RESISTOR.