Abstract: A method and an apparatus for compensating for aging and temperature of the crystal in a crystal oscillator. An RF signal which is transmitted by a mobile telephone switching office (MTSO) (108) and received by the antenna (118). The signal transmitted by the MTSO (108) serves as an external reference. A crystal-controlled main oscillator/time base generator (134) provides a local reference frequency to the converters (120) and provides a time base signal to a counter (136). A controller (112) reads an aging correction value from a memory and provides a frequency control signal to the main oscillator (134). The converters (120) convert the received RF signal to an IF frequency. A limiter (122) provides a limited IF signal to the counter (136). Counter (136) counts the number of cycles of the limited IF signal that appear in a cycle of the time base signal. A controller (112) compares this measured count to a reference count and the count error is determined.

Abstract: A transceiver (10) having a retractable antenna (12) that substantially reduces interference when the antenna is in a retracted position. The transceiver (10) includes transceiver circuitry (T), operating at a predetermined frequency, electrically connected to the retractable antenna (12). The retractable antenna (12) includes two antenna elements (20, 22). A first antenna element (20) comprises a whip antenna element, movable within a conductive tube (14) housed within a cellular telephone case (C). A second antenna element (22) comprises a helical coil antenna element extending from the whip antenna element (20) and located outside the case (C). In the retracted position, a first contact assembly (76) contacts the whip antenna element (20). The first contact assembly (76) is electrically connected to the transceiver circuitry (T) through a conductor (96) which is a predetermined multiple of a quarter wavelength at the predetermined frequency.

Abstract: A car radiotelephone system having one or more wireless handsets communicating voice and control information via an ultrasonic link with a stationary unit connected functionally to a base station. The base unit (1) is connected by two cables, an audio-out cable (a) connected to the radio frequency receiver (2) and an audio-in cable (b) connected to the radio frequency transmitter (3), to a stationary transmitting/receiving unit (4). The stationary transmitting/receiving unit consists of two summing amplifiers, transmitting summing amplifier (5) and receiving summing amplifier (6), and any number of ultrasonic transmitters and receivers. Likewise, any number of handsets can be used. The handsets (15) comprise an ultrasonic receiver (19), an ultrasonic transmitter (20), transmitter and receiver circuitry (27), a keypad (28), display circuitry (29), microphone (30), earpiece/speaker (31), and a rechargeable battery and ringer.