Abstract: A current mode active filter includes a differential amplifier, having two transistors, and a current mirror, having two transistors, connected into a feedback loop. The phase shift of the loop is controlled by one or two grounded capacitors and bias current sources connected to forward bias the base-emitter junctions of the transistors. The frequency of the filter is controlled by varying the dynamic resistances of the base-emitter junctions with the bias current sources. The current mirror increases loop gain, thereby enhancing the Q of the circuit. Improved dynamic range and large-signal performance can be achieved by the addition of two transistors to the current mirror circuit.

Abstract: A liquid crystal light emitting display (LCLED) device having two modes of operation. In the first mode the LCLED device produces dark symbols on a light background. In the second mode the LCLED device emits light producing light symbols on a dark background. The LCLED includes a LCD cell having an optically active nematic liquid crystal composition interposed between two parallel glass substrates. The glass substrates having transparent electrode indicia on the inner surfaces. Disposed on the outer surfaces of the glass substrates are polarizers having their axes of polarization orthogonal in the first mode, and their axes of polarization parallel in the second mode. A transparent panel having indicia identical to the electrode indicia is disposed on the exterior of one of the polarizers. The transparent panel is comprised of transparent material having fluorescent dye stuff. The transparent panel is optically connected to a light collecting means.

Abstract: A method and apparatus is disclosed for improving the quality of speech samples communicated via sub-band coding utilizing adaptive bit allocation, by providing error detection only on the adaptive bit allocation information. A first error detection code, such as a cyclic redundancy check (CRC), is calculated on the bit allocation parameters in the transmitter and sent to the receiver, where a second error detection code is calculated based upon the reconstructed bit allocation parameters. The transmitted error detection code is then used to determine if the received bit allocation information is correct, and if not, the frame of speech data is discarded. By protecting only the bit allocation information, additional speech frames may be salvaged from the error-prone channel, thus further increasing speech intelligibility.

Abstract: An battery powered, adaptive signal decoder is disclosed which is capable of processing detected encoded signals in accordance with a plurality of decoding schemes. The decoder has an equivalent microcomputer implementation. Energy conservation means operating independently of the detected signals acts to conserve the energy of the battery.

Abstract: A detachable low profile mounting clip arrangement suitable for use with a portable hand-held electronic apparatus such as a paging receiver, includes a housing having a slot. A base member has a hook attached to one end and a pair of apertures at the other end. The hook engages in the slot of the housing while the apertures spring over a pair of wedge shape protuberancies in the housing and snap into place. A mounting clip or lanyard is attached to the base member.

Abstract: An acknowledge back (ack-back) pager is provided for receiving paging signals from a central paging station. The central paging station transmits a group of message signals to a group of ack-back pagers which are addressed as a group. The users of the group of addressed ack-back pagers indicate a response to their respective pagers thus providing ack-back data. The pagers in the group of addressed ack-back pagers then simultaneously transmit back to the central station their ack-back data on different frequency sub-bands, a different frequency sub-band being dynamically allocated to each of the pagers in the group. Each ack-back pager determines whether the paging signals received thereby exhibits a signal level less than a predetermined threshold level. If the paging signals received by a particular ack-back pager exhibit a signal level less than such predetermined threshold level, then the pager transmits back to the central station at a first output power level.

Abstract: An acknowledge back (ack-back) pager is provide for use in a paging system which includes a central station which transmits a group of message signals to a group of ack-back pagers which are addressed as a group. The users of the group of addressed ack-back pagers indicate a response to their respective pagers thus providing ack-back data. The pagers in the group of addressed ack-back pagers then simultaneously transmit back to the central station their ack-back data on different frequency sub-bands, a different frequency sub-band being allocated to each of the pagers in the group. The invention provides apparatus for controlling the frequency of the selected sub-band with very high accuracy.

Abstract: An antenna tuning arrangement is provided for a miniature personal communications device which is normally worn on the body. The device includes a wristband having an antenna and antenna tuning elements which are normally concealed, to allow the antenna to be tuned while the device is being worn. A receiver in the communications device is coupled to the antenna and to a tuning indicator circuit which provides a tuning indication when the tuning element is adjusted without requiring entry into the device. The tuning indicator operation is selectable and draws no power when not selected.

Abstract: A spring clip arrangement is disclosed for a portable battery powered device which provides an efficient chassis retention feature for a slideably removable electrical chassis in unassociated housing. This retention is accomplished without machine screws and no special tools required. This spring clip arrangement also serves as the electrical contact interface for the associated battery power source insertable in a provided battery compartment.

Abstract: An antenna having provision for mounting to a printed circuit board and method for making the antenna is described. The antenna includes a generally elongate, magnetically permeable core having a major axis and an insulating substrate affixed along an axis parallel to the major axis. The insulating substrate has a plurality of opposed pairs of spaced conductive runners positioned at generally regular intervals along the substrate normal to the major axis. A plurality of discrete capacitors are and perpendicular to secured between the opposed pairs of conductive runners. An electrically conductive split sleeve substantially surrounds the core and has pairs of opposed tabs on the edge portions in electrical connection with the opposed pairs of conductive runners. The sleeve further includes integral mounting tabs for securing the antenna assembly to the printed circuit board to establish electrical connection to the antenna without the use of wire leads.

Abstract: Apparatus and method is disclosed for automatically, or by selective response, call forwarding a message to one or more system pagers which have an acknowledge back capability.In one embodiment, disclosed apparatus automatically forwards a message to another system pager upon the initially called pager failing to acknowledge back within a predetermined time period. Such other pager is determined from a set paging hierarchy included within the paging terminal apparatus itself.In another embodiment, wherein the system pagers have multiple acknowledge back response capability, a called pager can request the received message be additionally call forwarded to one or more other system pagers in accordance with the particular acknowledge back response chosen by the called pager user.

Abstract: A small closed loop antenna is formed by a flat metal member formed into a U-shape which also serves as the front, back and top surfaces, or parts thereof, of the housing for a portable communications receiver. Connected to the open (bottom) end of the arms is an isolation network providing an optimum antenna ground and a reactance network which applies a capacitive reactance across the antenna and isolation network so that the conductive member forms an antenna that detects the H-field of the electromagnetic wave to be received. The reactance network is tunable to adjust the antenna for reception at particular frequencies.

Abstract: An improved noise suppression system (800) is disclosed which performs speech quality enhancement upon the speech-plus-noise signal available at the input (205) to generate a clean speech signal at the output (265) by spectral gain modification. The improvements of the present invention include the addition of a signal-to-noise ratio (SNR) threshold mechanism (830) to reduce background noise flutter by offsetting the gain rise of the gain tables until a certain SNR threshold is reached, the use of a voice metric calculator (810) to produce more accurate background noise estimates via performing the update decision based on the overall voice-like characteristics in the channels and the time interval since the last update, and the use of a channel SNR modifier (820) to provide immunity to narrowband noise bursts through modification of the SNR estimates based on the voice metric calculation and the channel energies.

Abstract: A paging system providing an LPC encoded speech output having an adaptive bit rate. The LPC bit rate is adaptively modified based on paging system airtime loading. Synthesizer circuitry in the paging receivers, together with a system signaling scheme is used to update the paging receivers as to the LPC bit rate, allows the paging receiver to decode the adaptive bit rate signal.

Abstract: A paging system is provided having page transmission means responsive to a message origination device for transmitting selective call paging signals and messages. A query signal is also transmitted a predetermined minimum time period from the corresponding paging signal. A plurality of transceivers are provided responsive to the selective call paging signals and messages, and further responsive to the query signals for enabling the generating and transmitting of a response signal. Receivers are provided for receiving the transmitted response signals. The received response signals are then delivered to the message origination device from which the original message originated.

Abstract: A system transmitting synchronization signals and coded message signals is described. In particular, coded synchronization signals are used to indicate the transmission of coded message signals or the absence of transmission of coded message signals following the transmission of the coded synchronization signal, thereby providing a battery saving function for a personal communications receiver.

Abstract: A digital communication system for transmission and reception of speech signals and utilizing sampling, filtering and sub-band coding techniques for reduction of the bit rate. The energy levels of each sub-band are determined with respect to the band having the maximum energy level. The energy level information is encoded and divided into protected and unprotected bits. Only the protected bits are used for the determination of the bit allocation of the sample information, but both protected and unprotected bits are utilized in reconstituting the original levels of the bands.

Abstract: A personal message receiving apparatus is described including a portable communications receiver, intended to be carried by the user, which receives, detects and stores messages transmitted on a first radio frequency communication channel. The stored message is then subsequently transmitted over a second communications channel to a presentation unit having a second receiver which is intended to be carried by the user. The second receiver receives, and detects the message, and presents the message to the user in the form of a visual display. The message may also be stored.