Abstract: A self-contained, pre-pay coin operated telephone wherein when the user removes a handset from a switchhook, a local dial tone is generated, prompting the user to enter a telephone number of a called party. Once the first digit of that telephone number has been entered, the locally generated dial tone is removed and the user completes the entry of the telephone number. Once the proper coin has been deposited, the internal computer causes the telephone to couple itself to a central office. The telephone number entered by the user is then sent to the central office under control of the internal computer. During this time, the microphone in the handset is muted to disable communication. Once the user hears the called party answering, then the user must actuate a push-to-talk switch to indicate to the computer that the party has answered. The user is then allowed to speak to the called party and deposited coins are retained at the termination of the call.

Abstract: A high voltage switching circuit is provided for electrically coupling, or decoupling, a high voltage power supply to, or from, a load selectively in accordance with a control signal. The circuit converts the control signal to a radiant energy signal. A plurality of switching modules serially is coupled between the load and the high voltage power supply, each one of such modules including drive circuitry for converting the radiant energy into drive signals for a switching transistor which drives such transistor between a conducting and non-conducting condition selectively in accordance with the drive signal. With such arrangement, each of the modules develops its own drive signal in response to the radiant energy signal so that each drive signal is self-referenced to the reference potential of the module.

Abstract: A microwave frequency oscillator utilizing a push-push configuration to provide a low noise highly stable output signal at twice the frequency of a single resonator. The single resonator is connected in the feedback loop of two amplifiers. Additional circuit elements insure the proper oscillation conditions and relative phase are maintained. The use of a single resonator makes possible the application of various noise reduction techniques.