Apparatus for delivering an audible message from a vending machine in response to an operator activation

Claim 1

An audio annunicating system comprising: A. tape cartridge playback apparatus including an amplifier; B. a speaker coupled to said amplifier for audibly reproducing signals recorded on a tape cartridge when said tape cartridge playback apparatus is energized; C. a power source for said tape cartridge playback apparatus; D. a set of relay contacts in circuit with said power source and said tape cartridge playback apparatus; E. a relay coil for switching said relay contacts from a first position to a second position when an energizing signal is applied across said relay coil, only one of said first and second contact positions permitting energy flow from said power source to said tape cartridge playback apparatus; F. a momentary closure switch for instituting a cycle of operation of the audio annunicating system; and C. a timing circuit in circuit with said relay coil and responsive to the actuation of said momentary closure switch for changing the state of energization of said relay coil such that said relay contacts assume the position permitting energy flow from said power source to said tape cartridge playback apparatus, said timing circuit being coupled to said amplifier and responsive to the absence of a signal from said amplifier for a predetermined period to change the state of energization of said relay coil such that said relay contacts assume the position alternate to the one of said positions which permits energy flow from said power source to said tape cartridge playback apparatus, said timing circuit comprising: 1. a first amplifier stage, said first amplifier stage having input terminals and output terminals, said input terminals being coupled to said amplifiers in parallel with said speaker; 2. said first amplifier stage including a clipping circuit for limiting the amplitude of the signal thereto, said clipping circuit comprising back-to-back diodes disposed across said input terminals; 3. a second amplifier having input terminals and output terminals; 4. a low pass audio filter coupling said output terminals of said first amplifier stage to said input terminals of said second amplifier stage for attenuating tape hiss and noise in the higher audio frequencies from the signal; 5. a pulse-forming stage having input terminals and output terminals; 6. a resistor/capacitor charging circuit coupling the output terminals of said second amplifier stage to the input terminals of said pulse-forming stage, said capacitor charging and discharging equally when said second amplifier stage issues an amplified alternating signal; 7. means for charging said capacitor in a predetermined polarity in the absence of an alternating signal from said second amplifier stage; 8. said pulse-forming stage comprising an active element normally biased off and including means responsive to a predetermined minimum charge on said capacitor in said predetermined polarity to bias said active element momentarily on whereby a pulse issues from the output terminals of said pulse-forming stage; and 9. a silicon-controlled rectifier coupled in series with said relay coil for issuing said energizing signal to said relay coil, said silicon-controlled rectifier having a gate electrode coupled to said pulse-forming stage to receive pulses therefrom, said pulses firing said silicon-controlled rectifier causing said energizing signal to issue therefrom.