Abstract: A multiple latched accumulator fractional-N synthesizer for use in digital radio transceivers is disclosed. The divisor of the frequency divider (103) of the synthesizer is varied with time by the summation of accumulator carry output digital sequences which result in frequency increments equal to a fraction of the reference frequency. The accumulators (615, 617) are latched such that upon the occurrence of a clock pulse, data is transferred through each accumulator one clock pulse step at a time, such that the delay through the system is equal to that of only one accumulator. The carry outputs of each accumulator are coupled through delays (645, 647, 649, 631, 633) equal to one less delay than the number of accumulators and added (635) such that all higher order accumulator carry outputs add to a net summation of zero so as to not upset the desired fractional setting of the first accumulator.

Abstract: A fractional-division synthesizer for a digital transceiver is disclosed in which the fractional divisor may be separated into an integer, N, and a fraction made up of two integers, [n/d]. The integer n is the numerator of the fraction part of the fractional divisor. The integer N is the whole number portion of the fractional divisor. The integer d multiplied by the value of the transceiver channel spacing is algebraically related to the frequency of the reference oscillator. A bit rate clock is also derived from the reference oscillator.

Abstract: A PCM telephone switch that is simultaneously compatible with both DS-1 and CEPT PCM formats is disclosed. A switch module performs timeslot switching of individual subchannels between DS-1 and CEPT trunks which are input by way of digital group interfaces. Each group interface couples to one or more trunks of serial bit streams of either DS-1 or CEPT format standards. After the input serial bit stream is converted to a parallel format, it is used as eight bits of the address bits of data processing ROMs from which a corresponding 8-bit word is parallel read on a per channel basis and routed to the appropriate output data processing ROMs. The output data bits of the ROMs are the processed data bits which are reconverted to serial format for either DS-1 or CEPT standards as required by the output trunk. A-law or .mu.-law decoding and encoding is accomplished independently from input to output channel on a per channel basis.

Abstract: A battery charger having positioning and support apparatus for aligning batteries of varying sizes is disclosed. A recess in the battery charger housing has tapering sides which produce a charging pocket wider toward the front of the charger than toward the rear. Batteries of varying thickness have sloping sides which conform to the angle of taper of the battery charger. Rib members on the tapering sides engage slots in the batteries such that the batteries upon insertion into the charging pocket are initially guided by the tapering sides and then accurately positioned by the rib members.

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: A frequency synthesizer having a frequency divider and a frequency multiplier in the feedback loop is disclosed. The minimum frequency separation between two adjacent synthesized channels is equal to the reference frequency divided by the multiplication ratio of the multiplier. The division ratio of the frequency divider, which can be analyzed as the sum of an integer and a fractional portion, is varied with time by a digital sequence, resulting in a minimum frequency increment equal to a fraction of the reference frequency. The multiplier acts to reduce the nonlinearities of the frequency synthesizer when the fractional portion of the division ratio causes a large variation in the instantaneous division ratio by reducing the effective division ratio of the loop.

Abstract: In a PLL synthesizer, the tolerance to gain and component variations is greatly reduced when the gain of the loop in increased above that which the loop was initially designed for and if the third order loop symmetric ratio is reduced to a value within the range of 2.0 to 2.5. Higher order loops based on the third order symmetric ratio range have correspondingly lower transmission pole frequency to open unity gain frequency ratios.

Abstract: A bandwidth agile, dielectrically loaded resonator filter is disclosed in which conductive strips (320, 322), plated on the top surface (302) of the filter and disposed between resonators (310, 312, 314), are selectively switched to ground in order to affect a change in the bandwidth without appreciably changing the center frequency of the filter response. PIN diode switching networks (316, 318), including a means for biasing the diode, are used to effectively ground the strips between the nearly quarter-wavelength transmission line resonators contained within the block (300) of the filter, thereby capturing a portion of the capacitive coupling (402, 404) which occurs mostly beneath the surface of the filter between adjacent resonators.

Abstract: A fractional-N synthesizer employing at least a second order sigma-delta modulator is disclosed. The most significant bits from the output accumulator of the sigma-delta modulator are used as the carry out control for the variable divisor of the loop divider. Modulation to the synthesizer is introduced as part of the digital number input to the sigma-delta modulator and spurious signal output is reduced by selection of a large number as the denominator of the fractional portion of the loop divider divisor.

Abstract: A digital radio system having improved co-channel utilization is disclosed. A remote terminal receives a station identification from one of the fixed stations having an overlapping radio coverage area with another fixed station and retransmits this station identification with its message. A second fixed station receiving the remote terminal's transmission uses the station identification and the signal strength of the remote terminal to determine whether transmissions from other remote terminals should be inhibited. Depending upon the geographic proximity of the first fixed station to the second fixed station and the remote terminal's signal strength at the second fixed station, a signal representative of the remote terminal's signal strength at the second fixed station may be transmitted by the second fixed station. This representative signal may be used by a second remote terminal to determine whether the second remote terminal may transmit.

Abstract: A continuous speech recognition system employs a grammar tree of alternative potentially recognized word paths. A technique of tracing back through the grammar tree is utilized in determining which partial word path is common to all potential word paths. The common partial word path is deleted and words corresponding to the deleted partial word path are output as recognized words.

Abstract: A phase-locked loop system having as input a stable refernce clock signal and outputting a master clock signal. The phase of the stable reference clock signal is compared to that of the pre-scaled master clock signal and the difference represented by an analog error signal which is converted to a digital signal by an A/D converter (116). The digital signal is then transformed into an analog control signal by a D/A converter (120) and applied to a VCO (128) which generates the master clock signal, If the stable reference clock signal has degraded or is lost the A/D converter (116), which receives its sampling clock in part from the stable reference clock signal, stops sampling and thus stops producing digital signals. The last good digital signal is maintained, the last good analog control signal is maintained and thus the master clock signal is maintained.

Abstract: A multiple battery, multiple rate automatic switching battery charger is disclosed. Two or more batteries are charged sequentially in a multiple pocket battery chargers in order to maintain a low peak power consumption level. One battery pocket is assigned a priority so that a battery placed therein will be charged first at a fast rate of charge. Upon completion of the fast charge cycle, the priority battery can be trickle charged during the fast charge of the non-priority pocket battery.

Abstract: A radio arrangement and method allows a portable (210) and a mobile (212) to uniquely communicate on a radio system having at least one remote system site (114). The portable (210) has at least one information set (such as the radio's identification information and repertory dialing information) (356 or 360), and the mobile (212) is intercoupled therewith via a connector (214). The connector is used for transferring a code, which designates the information set, from the portable (210) to the mobile (212), whereby the mobile (212) adopts the information set of the portable (210) for subsequent communication. The arrangement offers an user having a portable, with its limited features and functions, to utilize all of the capabilities of the mobile.

Abstract: A radio frequency duplexer filter for a duplex transceiver is disclosed. To prevent spurious signals conducted by flyback responses of the transmit bandpass filter 103 from reaching the antenna (105), a band reject circuit consisting of third harmonic quarter-wave transmission line stubs (601 and 603) are advantegeously coupled to an output transmission line (107). Likewise, to prevent spurious signals conducted by flyback responses of the receive bandpass filter (113) from reaching the receiver (109), a band reject circuit consisting of third harmonic quarter-wave transmission line stubs (605 and 607) are advantageously coupled to an input transmission line (111).

Abstract: Word spotting in a speech recognition system without predetermining the endpoints of the input speech. The invention is intended to be implemented in a system which has word templates stored in template memory, with the system being capable of accumulating distance measures for states within each word template. The following steps are used to generate a measure of similarity between a subset of the input frames and a word template. The steps are: a) recording a beginning input frame number for each state to identify the potential beginning of the word; b) accumulating distance measures for at least one state for each input frame; c) normalizing the distance measures by substracting a normalization amount from each distance measure; d) recording normalization information corresponding to the normalization amount for each input frame; and e) determining a similarity measure between the word template and a subset of input frames after a given input frame has been processed.

Abstract: A battery charging system including a battery of one chemistry type and a battery charger for a different battery type is disclosed. If a battery over-discharge condition or if an electrochemical cell imbalance is detected within the battery, the battery prevents charging by the battery charger by means of a resettable switch.