Abstract: A low-power random digit generator for use with existing circuitry samples a changing physical variable. In a communications device, the random digit generator has an A/D converter that repetitively converts a received analog signal at a conversion rate, where a magnitude of the received analog signal changes at a received rate. At least one bit from the conversion is selected, and a random digital signal having a magnitude corresponding to the at least one bit is generated. The communications device preferably taps off an existing A/D converter and uses combinational circuitry to minimize power consumption.

Abstract: A two-way communication system for communication between a system network and a mobile unit. The system network includes a plurality of base transmitters and base receivers included in the network. The base transmitters are divided into zonal assignments and broadcast in simulcast using multi-carrier modulation techniques. The system network controls the base transmitters to broadcast in simulcast during both systemwide and zonal time intervals. The system network dynamically alters zone boundaries to maximize information throughput. The system also uses a mobile unit which receives messages from the network and transmits messages to the network. The mobile unit includes a switch that allows a user to request the network to retransmit a received message that contains errors.

Abstract: A method of multicarrier modulation using co-located transmitters to achieve higher transmission capacity for mobile paging and two-way digital communication in a manner consistent with FCC emission mask limits. Co-location of the transmitters obviates the need for stringent, symmetrical subchannel interference protection and provides for a wider range of operating parameters, including peak frequency deviation, bit rate, and carrier frequencies, to obtain optimal transmission performance.

Abstract: A ground-to-air telephone calling system is provided including a computer for receiving an airborne telephone number and a call-back number from a calling party and forming the telephone numbers into a data signal comporting with existing protocol filed in the FCC, an uplink unit for uplinking the data signal to a satellite and a plurality of downlink stations for receiving the data signal from the satellite; a plurality of ground stations corresponding to each of the downlink units for receiving the data signals and passing a call signal identifying the airborne telephone and particular ground station to a corresponding transmit/receive unit for subsequent transmission to the aircraft; a call being initiated from the ground station to the calling party over the public switched telephone network if the aircraft responds to the call signal.

Abstract: A mobile paging telephone call back device determines and adds the appropriate prefix to a received call back number. The call back device includes a pager, a control unit, an automatic dialer, and a cellular telephone. The pager receives a page message from a paging system central controller. The control unit extracts a dialable telephone number from the page message, determines the appropriate prefix to be added to the telephone number, and adds the prefix to the telephone number. Using the telephone number with the added prefix, the automatic dialer completes a call back for the cellular telephone.

Abstract: To ensure that a user of radio paging services receives page messages while traveling, page messages are broadcast over both the user's local paging channel and a nationwide paging channel during periods of scheduled travel. At all other times, page messages are broadcast over the user's local channel and accompanied by tone-only messages of abbreviated length broadcast over the nationwide channel. Receipt of a tone-only message provides user notification that he or she was paged over the local channel. Receiving logic in the pager carried by the user automatically switches the pager between local and nationwide channel frequencies under the control of channel marker codes transmitted over the local channel and a switching code included in tone-only messages received over the nationwide channel. To facilitate system management, all page messages are routed through a nationwide paging terminal.

Abstract: A ground-to-air telephone calling system is provided including a computer for receiving an airborne telephone number and a call-back number from a calling party and forming the telephone numbers into a data signal comporting with existing protocol filed in the FCC, an uplink unit for uplinking the data signal to a satellite and a plurality of downlink stations for receiving the data signal from the satellite; a plurality of ground stations corresponding to each of the downlink units for receiving the data signals and passing a call signal identifying the airborne telephone and particular ground station to a corresponding transmit/receive unit for subsequent transmission to the aircraft; a call being initiated from the ground station to the calling party over the public switched telephone network if the aircraft responds to the call signal.

Abstract: A system for establishing a communication link between a caller and a mobile communication device that includes a mobile telephone and a paging device capable of receiving information transmitted from a paging network. In addition to the mobile communication device, the system includes a telephone network, a first mobile switching center, a conference bridge, a paging network, and a second mobile switching center. The first mobile switching center receives a telephone call transmitted over the telephone network using an identification number of the mobile telephone. If the mobile communication device is not located in the area covered by the mobile switching center, the mobile switching center forwards the received telephone call to a conference bridge using a bridge number assigned to the mobile communication device. The conference bridge receives the forwarded telephone call and transmits an identification number of the paging device in the mobile communication device to the paging network.

Abstract: A ground-to-air telephone calling system is provided including a computer for receiving an airborne telephone number and a call-back number from a calling party and forming the telephone numbers into a data signal comporting with existing protocol filed in the FCC, an uplink unit for uplinking the data signal to a satellite and a plurality of downlink stations for receiving the data signal from the satellite; a plurality of ground stations corresponding to each of the downlink units for receiving the data signals and passing a call signal identifying the airborne telephone and particular ground station to a corresponding transmit/receive unit for subsequent transmission to the aircraft; a call being initiated from the ground station to the calling party over the public switched telephone network if the aircraft responds to the call signal.

Abstract: A ground-to-air telephone calling system is provided including a computer for receiving an airborne telephone number and a call-back number from a calling party and forming the telephone numbers into a data signal comporting with existing protocol filed in the FCC, an uplink unit for uplinking the data signal to a satellite and a plurality of downlink stations for receiving the data signal from the satellite; a plurality of ground stations corresponding to each of the downlink units for receiving the data signals and passing a call signal identifying the airborne telephone and particular ground station to a corresponding transmit/receive unit for subsequent transmission to the aircraft; a call being initiated from the ground station to the calling party over the public switched telephone network if the aircraft responds to the call signal.

Abstract: A paging system includes a digital switch, an interface processor, and a central computer. The interface processor voice prompts a caller to input a desired function code and in response, performs the desired function or instructs the digital switch to route the call to a different portion of the paging system which may include a voice mailbox unit for recording voice messages. The digital switch, in response to an instruction from the interface processor, can establish a telephone connection to an outside number for a caller already connected to the paging system.