×

Transmitter for wireless audible indication system

  • US 5,757,305 A
  • Filed: 10/09/1996
  • Issued: 05/26/1998
  • Est. Priority Date: 07/29/1994
  • Status: Expired due to Fees
First Claim
Patent Images

1. In combination with a wireless doorbell receiver having a wide band superregenerative detector coupled to a crystal filter, the superregenerative detector having a bandwidth about a carrier frequency, a wireless doorbell transmitter for use with the wireless doorbell receiver, the transmitter comprising:

  • a crystal oscillator which produces a first signal having a predetermined frequency, the crystal oscillator utilizing a first low frequency crystal to produce the first signal;

    a duty cycle limiting circuit, coupled to the crystal oscillator, which forms a pulsed signal by limiting the duty cycle of the first signal to be less than 25%; and

    a radio frequency oscillator, coupled to the duty cycle limiting circuit, which produces a carrier signal at the carrier frequency and whose amplitude is modulated in dependence upon the pulsed signal,wherein the superregenerative detector detects the carrier signal and produces a baseband output that is applied to the crystal filter, the crystal filter utilizing a second low frequency crystal to provide a narrow band of filtering about the predetermined frequency.

View all claims
  • 2 Assignments
Timeline View
Assignment View
    ×
    ×