Gerry Baby Products Company

Gerry Baby Products

Perran V Newman

Theodore B Freese

Dwight D Ifland

Gary C Lindenberger

Niel P Zeller

In a wireless sound monitoring system, ambient sounds are monitored by a microphone and transmitted over a phase or frequency modulated transmitter to a receiver. A sound actuated switch responsive to ambient sounds louder than a predetermined level turns the transmitter on and causes a hidden tone to be generated. A delay circuit caused the hidden tone to be terminated before the transmitter is turned off when the sound level decreases. In the receiver, a mute circuit responds to the hidden tone to control the output of a loudspeaker, and thus, the hidden tone prevents a squelch tail from being heard. The monitoring unit also includes a pulse generator to cause the hidden tones to be generated at regular intervals, but with short pulse widths. In the receiver, a mute delay circuit prevents the un-muting of the loudspeaker in response to these short pulses, but as long as the hidden tone pulses are detected within a predetermined period of time, a visual indicator, an LED, will light to show the proper operation of the system. Each hidden tone detected will cause the LED to blink momentarily; however, if the hidden tones are not detected, the LED will be extinguished and a distinctive audio tone will be generated to alert the user.

Wireless sound monitoring apparatus with subaudible squelch control

A wireless audio monitoring system includes a reassurance tone generator for providing the user with assurance that a receiving unit is within range of the monitoring unit's transmitter and that both are operating properly. The reassurance signal is a brief audible tone transmitted at regular intervals by the monitoring unit to the receiving unit. The reassurance tone is either injected as sound into the monitoring unit's microphone, as an electronic signal into the microphone's amplifier or directly into the transmitter. A typical reassurance tone is a quarter-second long audible tone that occurs every ten seconds. At the receiving unit, the user has the option of either hearing or not hearing the reassurance tone by either eliminating the tone itself or by muting the loudspeaker during the time the reassurance tone is being received. Alternatively, the reassurance tone is turned on or off at the monitoring unit by means of a radio control signal sent from the receiving unit.

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Cambridge, United Kingdom

Perran V Newman