Abstract: A method and associated circuitry for acquiring a channel of a set of frequency channels by a radio receiver. The radio receiver scans selected control channels and measures the power levels of signals generated upon the respective ones of the control channels and stores values. An attempt to effectuate a communication link with a transmitter which transmits a data signal upon one of the control channels is only attempted if the measured power level on such control channel increases beyond a certain amount. The tuning frequency of the tuning circuitry can be retuned when the tuning circuitry is initially tuned to receive a communication signal transmitted by a transmitter of a less-than-most desired network of transmitters according to a second embodiment.

Abstract: An apparatus, and associated method, for determining signal transmission quality levels of a discretely-encoded information signal received by a receiver. The signal strength of the received signal is calculated, and the levels of interference introduced upon the information signal is determined. The value of the signal strength is weighted by the amount of interference introduced upon the information signal. The resultant weighted signal forms the signal transmission quality level. The value of the signal transmission quality level is displayed to provide a user with a quantitative indication of the signal transmission quality level of the signal received by the receiver.

Abstract: Data transfer apparatus (211,213) for a radiotelephone peripheral using a time multiplexed data bus for communication with a bus master of the radiotelephone couples peripheral devices external to the radiotelephone and other user information inputting devices, such as a handset for a cellular mobile radiotelephone, to the radiotelephone's central processor and speech processor. The data transfer apparatus generates time slots in frame formats in which the information is sent over the data bus. The entire message, information bits and the header, sent in a time slot from a peripheral device to the bus master is used to determine bus contention. Bus contention resolution during the start-up of data bus operation sets the priority with respect to other data transfer apparati with which a peripheral device's data transfer apparatus is able to access the bus during normal operation.

Abstract: A fractional-N synthesizer realizes automatic frequency control by adding (509) a digital representation of a determined frequency offset to a digital representation of applied modulation to create the modulus control of a programmable frequency divider (203).

Abstract: A controller for a radiotelephone having the capability of operation in both a secure mode for call authorization and a nonsecure mode for user interface is disclosed. The nonsecure mode and secure mode of operation are both resident in a single microcontroller which runs the nonsecure operations until a requirement for the secure operation is requested during call placement. The nonsecure mode is disabled during the period of time the secure mode is operational and is reenabled upon completion of the secure mode operation. The secure mode cannot be accessed externally to the microcontroller.

Abstract: An analog frequency inversion scrambler employing an exchange of random number seeds between an originating scrambler and an answering scrambler to create two pseudo-random frequency hopping rolling codes has been disclosed. The rolling code used in one direction of a duplex channel is different than the rolling code in the opposite direction and each code is synchronized by periodic synchronization signals.

Abstract: A mobile radiotelephone (120) includes a microcomputer (220), speakerphone control circuitry (106) and mobile radio (112). Mobile radio (112) includes a transmitter (242), receiver (244) and a duplexer (243) for coupling the transmitter (242) and receiver (243) to the mobile antenna. In the transmit voice path, speakerphone control circuitry (106) includes switch (201), variable gain amplifier (202), compressor amplifier (203), switch (204), variable gain amplifier (205), and two registers (212-213). In the receive voice path, speakerphone control circuitry (106) includes variable gain amplifier (232), expander amplifier (233), switch (234), variable gain amplifier (235), switch (236) and two registers (216-217). Speakerphone control circuitry (106) also includes rectifier/filter (224), a companding analog-to-digital (A/D) converter (225), two latches (218-219), rectifier/filter (226) and two registers (214-215).

Abstract: A portable radiotelephone is disclosed in which an associated logic unit communicates via a data bus with an internal keypad and display and a detachable external keypad and display. Capability is provided for detecting the presence of the external keypad on the data bus and, in response to the detection, the information which would normally be communicated between the logic unit and the internal keypad and display is diverted to the external keypad and display. When the external keypad is detached from the data bus, communications between the logic unit and the internal keypad and display is reestablished.