Abstract: A method and an apparatus for selecting a cellular carrier frequency for accessing cellular airtime services based upon a list of preferred system identification codes (SIDs). A cellular telephone is programmed to accept into memory a list of preferred SIDs corresponding to carriers through which service is preferred. While any SID remains in a preferred list, the standard A/B system selection function is replaced by a substitute system selection function which includes only three carrier selection modes including the Home Only mode, the SID Only mode, and a Roam Saver mode. With the Roam Saver carrier selection mode, the cellular telephone first prefers service through a home carrier and then through a carrier broadcasting a SID matching a SID on the preferred list, but never denies service to emergency or non-emergency destinations if any SID is detected.

Abstract: A cellular telephone, in its most preferred embodiment, performs a method for notifying a digital cellular telephone user of an imminent communication disconnection. The preferred method includes, at least, generating at least one condition indication representative of at least one communication condition, analyzing the condition indication, determining whether a communication disconnection is imminent, enhancing quality of received communication signals when possible, and notifying the user of an imminent communication disconnection. Exemplary condition indications include, at least, continuous count and rate indications of frame checksum errors, insufficient quality frames, symbol errors, and chip errors, output power level indication, received signal strength indication, soft handoff status indication, other pilot signal indication, and current pilot signal strength indication.

Abstract: A method and an apparatus for searching code division multiple access pilot signal energies includes limiting a pilot signal window size above a lower limit and only analyzing search result data corresponding to an instructed pilot signal window size. A central processing unit instructs a searcher receiver within a mobile station modem application specific integrated circuit to search for pilot signal energies within an instructed pilot signal search window unless the instructed pilot signal window size is smaller than a pilot signal window size lower limit. In such a case, the pilot signal search window size is artificially designated as the pilot signal window size lower limit to prevent excessive search completion interrupts from over utilizing central processing unit resources.

Abstract: A cellular telephone, in its most preferred embodiment, performs a method for notifying a digital cellular telephone user of an imminent communication disconnection. The preferred method includes, at least, generating at least one condition indication representative of at least one communication condition, analyzing the condition indication, determining whether a communication disconnection is imminent, enhancing quality of received communication signals when possible, and notifying the user of an imminent communication disconnection. Exemplary condition indications include, at least, continuous count and rate indications of frame checksum errors, insufficient quality frames, symbol errors, and chip errors, output power level indication, received signal strength indication, soft handoff status indication, other pilot signal indication, and current pilot signal strength indication.

Abstract: A variable attenuator circuit provides variable attenuation responsive to received signal strength in a receiver to reduce intermodulation (IM) distortion. In a dual-mode frequency modulation/code division multiple access (FM/CDMA) cellular telephone implementation, the variable attenuator circuit decreases IM distortion by variably attenuating received radio frequency (RF) signals before an initial RF amplification stage to reduce the level of undesirable frequency mixing products. The variable attenuator circuit is turned on (activated) and off (deactivated) at a single, relatively low, input power level. An attenuator enable signal is also supplied from a logic unit of the mobile station to enable operation of the variable attenuator circuit throughout operation in a digital mode.

Abstract: An output power control system prevents saturation by limiting total output power and maintaining closed loop responsiveness for a radio telephone having closed loop and open loop gain control systems. The output power control system determines when total output power exceeds an output power trigger level and automatically enters a saturation prevention mode whereby total output power is reduced through modification of a closed loop power control register. In one embodiment, an output detector and an output comparator continuously monitor output power, and in another embodiment, an analog-to-digital converter samples output power levels.

Abstract: In a synchronous fixed frame boundary system with variable data rates, a transmitter inserts into a current frame an indication of the data rate of the next frame. After the first frame is received and processed at a receiver, the data rates of subsequent frames are known before processing, thereby reducing processing load. Furthermore, because the rate indication is inserted into the frame to be error protected along with the rest of the frame information, reliability is high, while additional data overhead and complexity are very low. As an example, North American code division multiple access digital cellular telephone systems utilize variable data rate transmissions. As a station modem (SM) assembles a current frame for convolutional encoding and further processing, the SM inserts a rate indication for the subsequent frame in accordance with information from a vocoder and CPU of the appropriate data rate for the subsequent frame.

Abstract: A circuit for connecting multiple signal paths within a multi-mode communication device includes a double balanced mixer circuit selectively functioning as a modulation switch during an unbalanced state. As applied to a transmit section of a CDMA/FM cellular telephone, a dual-function double balanced mixer circuit connects a CDMA IF signal path with an FM audio signal path. The double balanced mixer circuit includes a double balanced mixer connected through oscillator input to an external LC (inductor-capacitor) tank connected to both a PLL (phase lock loop) and an FM audio signal. One signal input of the double balanced mixer receives a CDMA low IF signal, while the other double balanced mixer signal input is connected to a microprocessor-controlled switch for selectively unbalancing the balanced mixer while in the FM mode of operation.

Abstract: A method and an apparatus for searching code division multiple access pilot signal energies includes limiting a pilot signal window size above a lower limit and only analyzing search result data corresponding to an instructed pilot signal window size. A central processing unit instructs a searcher receiver within a mobile station modem application specific integrated circuit to search for pilot signal energies within an instructed pilot signal search window unless the instructed pilot signal window size is smaller than a pilot signal window size lower limit. In such a case, the pilot signal search window size is artificially designated as the pilot signal window size lower limit to prevent excessive search completion interrupts from over utilizing central processing unit resources.

Abstract: A closed loop AGC circuit for a digital side of a dual mode cellular telephone wherein receiver and transmitter adjustable amplifiers are controlled by a linear feedback control system including a linear signal level detector which determines signal levels after a receiver baseband demodulator stage. The linear signal level detector receives a signal at an AC signal level and produces, through an averaging process, a DC received signal strength indication at a DC signal level which is linearly proportional to the AC signal level. The received signal strength indication is compared to a reference signal to produce a gain control signal which is linearly inverted and supplied as a receive gain control signal to the receiver adjustable amplifiers. The gain control signal is also combined with a transmit adjust signal received from the base station and supplied as a transmit gain control signal to the transmitter adjustable amplifiers.

Abstract: A phase-locked loop (PLL) frequency synthesizer is connected in reverse to a reference signal and a controlled oscillator loop including a low pass filter and a voltage-controlled oscillator (VCO). Rather than receiving a reference signal through a reference oscillator input and a VCO output signal through a VCO input, the PLL frequency synthesizer receives a reference signal through the VCO input and receives the VCO output signal through the reference oscillator input. Additionally, the output of the PLL is taken from the buffered reference output, thereby eliminating the need for an external buffer. Accordingly, the data loaded into the PLL frequency synthesizer accommodates the reversed input scheme by altering the divide ratios and inverting the phase detector output signal.

Abstract: In a synchronous fixed frame boundary system with variable data rates, a transmitter inserts into a current frame an indication of the data rate of the next frame. After the first frame is received and processed at a receiver, the data rates of subsequent frames are known before processing, thereby reducing processing load. Furthermore, because the rate indication is inserted into the frame to be error protected along with the rest of the frame information, reliability is high, while additional data overhead and complexity are very low. As an example, North American code division multiple access digital cellular telephone systems utilize variable data rate transmissions. As a station modem (SM) assembles a current frame for convolutional encoding and further processing, the SM inserts a rate indication for the subsequent frame in accordance with information from a vocoder and CPU of the appropriate data rate for the subsequent frame.

Abstract: A phase-locked loop (PLL) frequency synthesizer is connected in reverse to a reference signal and a controlled oscillator loop including a low pass filter and a voltage-controlled oscillator (VCO). Rather than receiving a reference signal through a reference oscillator input and a VCO output signal through a VCO input, the PLL frequency synthesizer receives a reference signal through the VCO input and receives the VCO output signal through the reference oscillator input. Additionally, the output of the PLL is taken from the buffered reference output, thereby eliminating the need for an external buffer. Accordingly, the data loaded into the PLL frequency synthesizer accommodates the reversed input scheme by altering the divide ratios and inverting the phase detector output signal.

Abstract: A method and an apparatus for selecting a cellular carrier frequency for accessing cellular airtime services based upon a list of preferred system identification codes (SIDs). A cellular telephone is programmed to accept into memory a list of preferred SIDs corresponding to carriers through which service is preferred. While any SID remains in a preferred list, the standard A/B system selection function is replaced by a substitute system selection function which includes only three carrier selection modes including the Home Only mode, the SID Only mode, and a Roam Saver mode. With the Roam Saver carrier selection mode, the cellular telephone first prefers service through a home carrier and then through a carrier broadcasting a SID matching a SID on the preferred list, but never denies service to emergency or non-emergency destinations if any SID is detected.

Abstract: A modular plug and cover therefor includes a plug body having an insert portion and a rear portion having an indentation. The rear portion receives a cable for connection to the insert portion. A cover for the modular plug is of a substantially rectangular configuration having an open end fitting over the rear portion of the plug body. The cover portion is engageable with the plug body such that an enclosed space is defined between an end of the rear portion of the plug and an opposing inner wall of the cover. The cover is further provided with a tapered projection on an inner surface thereof which corresponds to the location of the indentation and an access opening through which a cable connected to the modular plug is passed. The cover portion may also be engaged with the plug in an inverted state to change the direction in which the cable is oriented.

Abstract: A modular plug and cover therefor includes a plug body having an insert portion and a rear portion having an indentation. The rear portion receives a cable for connection to the insert portion. A cover for the modular plug is of a substantially rectangular configuration having an open end fitting over the rear portion of the plug body. The cover portion is engageable with the plug body such that an enclosed space is defined between an end of the rear portion of the plug and an opposing inner wall of the cover. The cover is further provided with a tapered projection on an inner surface thereof which corresponds to the location of the indentation and an access opening through which a cable connected to the modular plug is passed. The cover portion may also be engaged with the plug in an inverted state to change the direction in which the cable is oriented.

Abstract: A remotely programmable radiotelephone and a remote programming unit. The radiotelephone (10) includes a receiver front end and demodulator (23), receiver signal processing circuits (30), a dual-tone, multiple-frequency converter (31), a controller (50), and a memory (51). The converter (31) converts DTMF tones into digital signals. The controller (50) monitors the output of the converter (31). If the output corresponds to a valid command then the controller (50) executes the command. Certain commands must be preceded by the user entering an access code using a control keypad (56) and by the reception of DTMF tones corresponding to a password or security code stored in the memory (51). Some commands cause telephone numbers to be stored in the memory (51) for later recall by the user. Other commands cause a number to be stored and an outgoing call to be automatically initiated.