Abstract: A portable frequency modulation transmitter (1) for voice or data is disclosed for operation at infrared frequencies. The transmitter comprises keyboard (200) or microphone (402) input capability and dual modes of use. In the data mode, carrier is generated when the keyboard is operated and is not generated when the keyboard is idle in order to conserve power. In the voice mode, either voice or data may be transmitted, data having priority over voice. A series connection of two variable modulus counters (302, 303) and other counters (304, 305, 306) provide a frequency shift keyed data signal, marker data signal, marker data frames between data frames, parity insertion and other features. In the event that the local battery power level falls below a particular level, a particular word is inserted in the applied binary data input.

Abstract: A portable frequency modulation transmitter (1) for voice or data is disclosed for operation at infrared frequencies. The transmitter comprises keyboard (200) or microphone (402) input capability and dual modes of use. In the data mode, carrier is generated when the keyboard is operated and is not generated when the keyboard is idle in order to conserve power. In the voice mode, either voice or data may be transmitted, data having priority over voice. A series connection of two variable modulus counters (302, 303) and other counters (304, 305, 306) provide a frequency shift keyed data signal, marker data signal, marker data frames between data frames, parity insertion and other features. In the event that the local battery power level falls below a particular level, a particular word is inserted in the applied binary data input.

Abstract: A noise detector and data signal receiver for a frequency modulation system has a first phaselock loop circuit (300), responsive to the received signal, for providing a signal indicative of the noise level and a first stage of demodulation of the received signal. A high speed comparator (330) of the first phaselock loop circuit provides a 90 degree phase-shifted signal which exhibits lesser delay and is substantially in phase with the input. Accordingly, the noise detection capability of the phaselock loop circuit (300) is improved. A second phaselock loop (200), also responsive to the received signal, extracts a voice signal from the received signal. A third phaselock loop (400) responsive to the once demodulated output signal of the first phaselock loop (300), extracts a digital data signal from the received signal. Squelch circuits (120, 121), activated at separate particular levels of noise, are responsive to the noise level indicator signal of the first phaselock loop.

Abstract: A hands-free telephone system is disclosed utilizing an infrared transmitter and receiver to permit wireless speech transmission. The transmitter uses frequency modulation imposed on the infrared signal and includes carrier shift signaling arrangements for indicating a low battery condition and transmitter turn-off. The receiver utilizes a noise detection circuit for permitting remote turn-on, for squelching noise in the voice path, and for feeding an alerting signal to a loudspeaker to indicate that the received signal is excessively noisy. The portable transmitter must then be moved or redirected to provide a better line-of-sight signaling path.

Abstract: A hands-free telephone system is disclosed utilizing an infrared transmitter and receiver to permit wireless speech transmission. The transmitter uses frequency modulation imposed on the infrared signal and includes carrier shift signaling arrangements for indicating a low battery condition and transmitter turn-off. The receiver utilizes a noise detection circuit for permitting remote turn-on, for squelching noise in the voice path, and for feeding an alerting signal to a loudspeaker to indicate that the received signal is excessively noisy. The portable transmitter must then be moved or redirected to provide a better line-of-sight signaling path.

Abstract: A hands-free telephone system is disclosed utilizing an infrared transmitter and receiver to permit wireless speech transmission. The transmitter uses frequency modulation imposed on the infrared signal and includes carrier shift signaling arrangements for indicating a low battery condition and transmitter turnoff. The receiver utilizes a noise detection circuit for permitting remote turn-on, for squelching noise in the voice path, and for feeding an alerting signal to a loudspeaker to indicate that the received signal is excessively noisy. The portable transmitter must then be moved or redirected to provide a better line-of-sight signaling path.