Audible indicator circuit

Claim 1

AN AUDIBLE INDICATOR CIRCUIT COMPRISING A VOLTAGE SOURCE, AN INPUT TRANSISTOR HAVING BASE, EMITTER AND COLLECTOR ELECTRODES, A FIRST VARIABLE IMPEDANCE CIRCUIT CONNECTED BETWEEN SAID BASE ELECTRODE AND A FIRST TERMINAL OF SAID VOLTAGE SOURCE, A SECOND VARIABLE IMPEDANCE CIRCUIT CONNECTED BETWEEN SAID EMITTER ELECTRODE AND A SECOND TERMINAL OF SAID VOLTAGE SOURCE, A MULTIVIBRATOR HAVING A PAIR OF TRANSISTORS EACH PROVIDED WITH BASE, EMITTER AND COLECTOR ELECTRODES, MEANS CONNECTING SAID LASTNAMED EMITTER ELECTRODES, MEANS CONNECTING SAID LASTPEDANCE MEANS RESPECTIVELY CONNECTING SAID LAST-NAMED COLLECTOR ELECTRODES TO SAID FIRST TERMINAL, A PAIR OF CAPACITORS RESPECTIVELY CONNECTED TO CROSS-COUPLE SAID LASTNAMED BASE AND COLLECTOR ELECTRODES OF THE PAIR OF MULTIVIBRATOR TRANSISTORS, THE VALUES OF SAID IMPEDANCE MEANS AND CAPACITORS BEING SUCH AS TO CAUSE SAID MULTIVIBRATOR TO OSCILLATE AT AN AUDIO FREQUENCY, MEANS CONNECTING THE ELECTRODE OF A FIRST ONE OF SAID MULTIVIBRATOR TRANSISTORS, ELECTRODE OF A FIRST ONE OF SAID MULTIVIBRATOR TRANSISTORS, AN AMPLIFIER TRANSISTOR HAVING BASE, EMITTER AND COLLECTOR ELECTRODES, MEANS DIRECTLY ELECTRODE OF THE SECOND ONE OF ELECTRODE TO THE COLLECTOR ELECTRODE OF THE SECOND ONE OF SAID MULTIVIBRATOR TRANSISTORS, SAID COLLECTOR ELECTRODE OF THE SECOND MULTIVIBRATOR TRANSISTOR HAVING A FIRST POTENTIAL WHEN THE MULTIVIBRATOR IS NOT OSCILLATING OF A VALUE TO BIAS SAID LAST-NAMED BASE ELECTRODE FOR RENDERING SAID AMPLIFIER TRANSISTOR SUBSTANTIALY IN A CUTOFF CONDITION AND HAVING ALTERNATE FIRST AND SECOND VALUES OF POTENTIAL WHEN THE MULTIVIBRATOR IS OSCILLATING TO ALTERNATE THE BIAS OF SAID LAST-NAMED BASE ELECTRODE FOR ALTERNATELY RENDERING SAID AMPLIFIER TRANSISTOR IN A CURRENT-CONDUCTING SIGNAL-AMPLIFYING CONDITION, IMPEDANCE MEANS CONNECTED BETWEEN THE LAST-NAMED EMITTER ELECTRODE AND SAID SECOND TERMINAL, A LOUDSPEAKER CONNECTED BETWEEN THE LAST-NAMED COLLECTOR ELECTRODE AND SAID FIRST TERMINAL, AND MEANS FOR VARYING THE IMPEDANCE OF AT LEAST ONE OF SAID VARIABLE IMPEDANCE CIRCUITS THEREBY CAUSING SAID MULTIVIBRATOR TO OSCILLATE AND PRODUCE AN AUDIBLE SOUND AT SAID LOUDSPEAKER.