Abstract: A warning system comprises a receiver adapted to receive and recognize a coded signal, and upon reception and recognition thereof to generate a warning signal; and a transmitter selectively actuable to transmit a coded signal receivable and recognizable by the receiver and including a monitor for monitoring the presence of an extraneous signal originating from another transmitter, the transmitter delaying transmission of the coded signal upon detection of the extraneous signal.

Abstract: An improved radio paging system providing automatic acknowledgment of message delivery, including a base station with spatially directive reception means and a pager capable of transmitting acknowledgment signals. The spatially directive reception means at the base station enhances the reception quality of the acknowledgment signals transmitted by the pager over that obtainable with conventional omnidirectional reception means, thereby compensating for the disparity in the base station and pager transmission powers.

Abstract: A method of conducting an intercom communication between two cordless telephone handsets is disclosed wherein a handset requests that the base unit designate the handset with temporary master status upon initiation of an intercom communication. The responsibility of providing master system timing is transferred from the base unit to the handset for the duration of the intercom call. Upon conclusion of the intercom call the responsibility of providing master system timing is returned to the base unit.

Abstract: In a CDMA communication network, each base station (BS) is made to establish synchronism between a downward transmission signal directed to a mobile station (MS) and an upward reception signal received from the mobile station by adjusting in the mobile station a mobile generated SS pattern into an adjusted SS pattern of producing an upward transmission signal for reception at the base station as the upward reception signal. In order to get the adjusted SS pattern, the base station inserts in the downward transmission signal an inserted signal representative of a propagation delay t(D) between the base and the mobile stations and a propagation delay increment t(d) while the mobile station is in a prelminary state of receiving the downward transmission signal as a downward reception signal first from the base station and is in a steady state, respectively. The signals may ba propagated through at least one communication satellite.

Abstract: In a method for controlling a burst output timing in a satellite communication system for performing radio communication between a central earth station and a plurality of remote earth stations via a satellite, the time between a transmission of burst data from each of the remote earth stations to the central earth station via the satellite and the reception of the burst data returned from the central earth station via the satellite is time-counted. The output timing of the burst data transmitted from each remote earth station is adjusted, when the burst data is to be sent to the central earth station, in accordance with a time difference between the time and a preset reference time. A burst output timing control system is also disclosed.

Abstract: A method for establishing inter-base-station synchronization among a plurality of radio base stations of a mobile radio communication system. Each radio base station transmits a radio frequency control signal including priority information identifying the priority of the transmitting station as it relates to establishing synchronization, and synchronization establishing information indicating whether synchronization has been previously established between the transmitting base station and any other radio base station.

Abstract: A network management system and method in a telecommunications network for selectively accessing a plurality of synchronization sources of varying levels of accuracy, availability, and cost, and for enabling individual subscribers to select which synchronization source they utilize for each service application. Alternatively, the network management system may dynamically provide each subscriber with the least expensive synchronization source having the required level of accuracy for the subscriber's selected application.

Abstract: A system for providing enhanced multi-function, simplex or duplex RF wireless coverage of a service area, while operating at gigahertz frequencies, employing audio, video or telemetry programming, or any combination thereof; using AM, FM, Digital or Single Sideband modulation, or any combination thereof; from multiple transmitting sites located in a pattern around the outer perimeter of the service area to be provided coverage. All RF transmitter stations assigned to a given service area are fed substantially identical programming with each station employing a directional transmitting antenna thus producing a service area and thereby providing the basic implosion characteristics of the system. A highly directional antenna is employed at each customer's receiving location focused on its optimum transmission site. System vertical, horizontal or circular antenna polarization compatibility provides service area coverage consistent with minimum interference and signal distortion.

Abstract: A system and method for spatially and temporally synchronizing satellite (space based) and terrestrial (ground based) communications services using time division multiple access between the two types of service providers is given. Satellite and terrestrial communication services are assigned geographic cell boundaries to prevent conflicting simultaneous use of allocated spectrum. The spatial synchronization of cell boundaries can occur before hand by agreement between the users of the satellite and terrestrial services. This spatial synchronization may conform to geographic as well as political boundaries. Satellite and terrestrial services are assigned time slots to use a given spectrum within a given area. Methods are described for synchronizing the time slots to prevent interference between the services. Synchronization of LMDS and Teledesic services is described in the disclosure of a preferred embodiment.

Abstract: Transmitters (18) in a two-way radio communication system (10) transmit location inquiries to subscribing pagers (14), each transmission occurring at a given power output level. Each pager (14) is capable of responding with an acknowledgment signal identifying a particular transmitter whose signal was captured. Messages are sent to those pagers which respond with proper acknowledgments. To locate a pager which failed to acknowledge receipt of a signal from a particular transmitter, the power output level of at least one transmitter, and preferably a group of transmitters, is changed, and the transmitters re-transmit the location inquiry at the changed power output levels. A similar power-shifting technique is provided for transmitters in a one-way communication system.

Abstract: A paging system includes a satellite uplink (40) for assembling paging information and transmitting it to a satellite (26). The satellite (26) is then operable to transmit in a simulcast manner all the information to various regional paging systems (42). Each of the paging systems (42) includes a plurality of towers (10) each containing a satellite receiver (50), a satellite dish (48) associated therewith and a paging transmitter (52). Each of the satellite receivers (50) are operable to receive the information transmitted from the satellite (26) at substantially the same time such that there is no phase difference between any of the towers, regardless of location. Therefore, the transmitters (50) can transmit through antennas (12) information at the paging frequency with substantially no relative delays relative to each of the antennas (12). A backup link receiver (28) is provided for interfacing with a backup link transmitter (70).

Abstract: A portable radio (104) initiates a communication link using a synchronous protocol format. A base station (102) generates a synchronization pattern (200) which includes a marker. The marker (202) includes a generic code that invites portables to make link requests. The portable radio (104) synchronizes to the marker (202) and recognizes the generic code that indicates base availability. The portable radio (104) sends a link request in response to the generic code to initiate the communication link, and the base station (102) grants a link in order to establish the communication link.

Abstract: A global radio paging system in which a plurality of radio frequency carriers having the same frequency are synchronously modulated in a plurality of base stations corresponding in number to the radio frequency carriers with the same digital paging signal and transmitted, respectively. A paging controller which receives paging calls through a public switched telephone network stores preliminarily the maximum value of a sum of a paging request signal transmission time in a transmission line and a time required to process the paging request signal in each of the base stations and a high precision time signal is produced on the basis of a reference signal from a GPS (Global Positioning System) satellite. A transmission time assigning code is attached to the paging request signal, which assigns a time instance which is delayed from a current time determined by the high precision time signal by the maximum value of the sum of the transmission time and the processing tame as a transmission start time.

Abstract: An apparatus for the detection of information expected to be present in a defined data block of a RDS data flow transmitted as a predetermined number of groups which periodically follow one another, with a radio receiver tuned-in one after the other to a number of senders to be tested and whose RDS decoder is synchronized with the RDS data flow of the respective tuned-in sender. A running counter is provided having the frequency of the RDS data cycle and which is respectively reset upon reaching a count status corresponding to the period of a number of groups.

Abstract: An apparatus and a method in a radio communication system repeatedly transmit and receive identifiers including a nearby identifier received by a radio receiver from a nearby transmitter, and distant identifiers received from more distant transmitters. The method and the apparatus distinguish in a probabilistic manner the nearby identifier from the distant identifiers by determining the identifier received most dependably over a predetermined period.

Abstract: A communication system (100) provides simultaneous synchronization between a network controller (106) and numerous radio ports (102) using a single signaling channel. The network controller (106) includes a multiframe synchronization generator (208) which generates a multiframe synchronization packet (302) in response to a series of counters (212) and a timing reference (202). Each radio port (102) includes a multiframe synchronization detector (410) which verifies that the multiframe synchronization packet (302) is error free.

Abstract: An apparatus and method synchronizes a communication frame of a newly added base station, in a Time Division Multiple Access (TDMA) communication network, to communication frames in the existing communication network of base stations by operating the newly added base station to receive down link signals of a neighboring active base station and synchronize its receive slot in the communication frame with a corresponding forward time slot of the communication frame of that base station. The receive time slot of the newly added base station is shifted by an offset reference time to establish it own forward time slot. The offset reference time is determined by the time interval required for the base station to change from a forward to a reverse channel.

Abstract: A network control system for eliminating a relative error among control signals transmitted from nodes provided in radio zones respectively, a mobil station moving among the radio zones, each of the nodes comprising: a relative error detecting unit for detecting a relative error between an after-controlled transmitting control signal to be transmitted to adjacent nodes and a received control signal from an adjacent node; and a control unit for controlling a before-controlled transmitting control signal in such a way that the relative error becomes zero so as to output the after-controlled transmitting control signal.

Abstract: A network control system for controlling a plurality of nodes respectively corresponding to, and provided in, a plurality of radio zones. Each node has a corresponding base station, where a mobil station travels among the plurality of radio zones and communicates with the base station of a respective node when travelling in a radio zone corresponding to the respective node. Each base station transmits a transmission signal for the corresponding node to adjacent nodes, receives transmission signals transmitted from the base stations of adjacent nodes and spatially filters the received transmission signals.

Abstract: A fixed system receiver (107), which includes a forward receiver (305), a reverse receiver (310), and a response timer (215), is for use in a radio communication system (100) having a forward radio channel and a reverse radio channel. A command is transmitted in a forward channel radio signal to a selective call transceiver. The forward receiver (305) is for receiving, demodulating, and decoding the command. The reverse receiver (310) is for receiving and demodulating the reverse channel radio signal. The response timer (215), which is coupled to the forward receiver (305) and the reverse receiver (310), is for determining a response period beginning substantially at a scheduled response time included in the command and having a duration which is substantially a designated length of the data unit included in the command, and for generating a control signal which enables the reverse receiver (310) during the response period.

Abstract: The base stations (BS) in a multicellular, wireless telephone system are connected via trunk lines (VL) to a communication system (KS), particularly to a telephone private branch exchange. The base stations (BS) are arranged at such a distance from one another that synchronization information (si) wirelessly transmitted from one base station (BS) can be at least partially received in a neighboring base station (BS). Both the initial, wireless synchronization as well as the synchronization during operation are controlled by the communication system such that respectively one base station (BS) is synchronized to the synchronization information (si) transmitted from a neighboring base station (BS). Compared to a synchronization of the base stations (BS) via trunk lines (VL), these deviations due to running times and different processing speeds in the synchronization unit realized in circuit-oriented terms are avoided in the wireless synchronization.

Abstract: This invention provides a method for substantially reducing the time drift f a network clock in a frequency hopping communications system, without the need for a master unit to keep network time. The automatic network time tracking mechanism of each receiver is disabled when a network time update is received within a critical period of time from the closest synchronization update time or frequency hop time. The critical period is defined as the time between the closest synchronization update time to the local time when reception occurs less one-half the minimum tracking adjustment of the receiver plus the minimum processing or decoding delay, and that closest synchronization update time plus one half the minimum tracking adjustment of the receiver plus the maximum processing or decoding delay.

Abstract: Transmission of candidate-sector signalling channels are synchronized to facilitate mobile-assisted handoff (MAHO) measurements by a mobile (125). Transmitters in candidate sectors each transmit their signalling channel at distinct frequencies and at predetermined intervals. The transmission of each signalling channel by each candidate sector transmitter is synchronized to provide a known reference to the mobile (125). When instructed, the mobile (125) need only to perform MAHO measurements at the predetermined intervals in the order and at the frequency instructed.

Abstract: A network control system for controlling a plurality of nodes respectively corresponding to, and provided in, a plurality of radio zones. Each node has a corresponding base station. A mobil station travels among the plurality of radio zones and communicates with the base station of a respective node when travelling in a radio zone corresponding to the respective node. Each base station transmits a transmission signal to adjacent nodes and receives transmission signals transmitted from the base stations of adjacent nodes.

Abstract: Methods for provision of a sequence of timing signals for one or a plurality of microprocessors, microprocessor peripheral devices or other timing-controlled instruments ("users"), using timing signals determined from a Satellite Positioning System (SPS), such as GPS or GLONASS. In a first embodiment, one or a plurality of users is individually provided with SPS signal antennas and receiver/processors, and timing signals are optionally individually for each user. The timing signals can be periodic, for example, a One-Pulse-Per-Second signal for fine corrections of high frequency timing signals issued by an internal or external clock. The timing signals can also be substantially non-periodic. The timing signals may also be used to determine the time at which selected events occur, such as issuance of interrupt commands in, or directed to, a microprocessor.

Abstract: A radio apparatus having a unit for receiving a first signal from a first transceiver compressed in time by a predetermined rate, a unit for reproducing a first original signal from the first signal, a unit for receiving a second signal from a second transceiver compressed by the predetermined rate during the reception period of the first transceiver, a unit for reproducing a second original signal from the second signal, and a unit for adding the first and second original signals and outputting the added signal.

Abstract: A location monitoring system is provided having a radio frequency transmitter for a person or object and radio frequency receiver for someone to monitor movement of the person or object, the receiver sounding an alarm at a predetermined time after failure to receive a signal. The transmitter is made having an intermittent transmitted signal and the receiver is made having an off-timer to coordinate with the intermittent signal, the off times saving battery power. The radio frequency receiver has an electronic switching device controlled by the radio frequency transmitter for sounding an alarm. An antenna is located in part of the carrying strap of the transmitter. The radio frequency transmitter can have various devices for sounding the alarm.

Abstract: A method at comparator (103) of determining the depth of remote buffer (107-109), by computing the difference between the current time and a next launch time, where the next launch time is the time at which a next information packet will be transmitted by the base station (104-106) on the radio channel. The next launch time is determined by the summation of, the time to transmit a previous information packet with error correcting information on the radio channel, and the launch time of a previous information packet. The method further includes maintaining the buffer depth between thresholds such that information packets will not be provided beyond a maximum threshold and filler packets will be provided when buffer depth is less than a minimum threshold.

Abstract: In a cellular network, a multiple-access methodology and concomitant circuitry in which TDMA is used inside each cell and CDMA signals, having pulse shapes with low cross-correlations, are assigned to adjacent cells. For example, these pulses could be Direct-Sequence Spread-Spectrum pulses. Such a hybrid system combines the high intra-cell capacity of TDMA with the inter-cell and multipath interference rejection capabilities of CDMA.

Abstract: A communication system that performs time-division multiple access mobile communication using radio in a service area in which are disposed a plurality of base stations connected to a central station through a communication network. The central station selects and designates a master base station and a selected base station close to the master base station. The central station instructs the selected base station to synchronize a radio signal transmitted by the selected base station with a radio signal transmitted by the master base station. The central station further selects at least one additional base station close to the selected base station. The central station instructs the at least one additional base station to synchronize a radio signal transmitted by the additional base station with a radio signal transmitted by the selected base station. The process is repeated until all of the base stations are transmitting a synchronized radio wave.

Abstract: Processing of dispatch calls in a simulcast multi-site communication system begins when a source communication unit transmits a message to one or more network receivers. The received signals are analyzed immediately at the received sites for signal quality. Each of the signals are time stamped to identify when they where received. The received signals are transported with their time stamp and signal quality metric to each of the other sites via a digital communication network connecting the sites. A master transmitter site determines the receiver source with the best quality signal as indicated by the signal quality metric. The master transmitter then transports the chosen best quality signal to each of the other sites via a digital communication network. Each transmitter site performs a transmit operation by storing the chosen best quality signal until it is time to transmit the signal in phase with all the other transmitter sites in a simulcast manner.

Abstract: A coherent reverse channel, a per-chip spreading function, orthogonal spreading functions and a time alignment of all traffic channels are implemented such that the main signal of each channel arrives at a base-station within a fraction of a chip of one another in accordance with the invention. With this, the orthogonality among all channels is maintained, and, when demodulated, all channels except the channel of interest provides a cross-correlation of substantially zero with respect to the remaining signals.

Abstract: An adaptive paging system includes a paging terminal that is operable to receive paging signals and transmit them up to a satellite (28) and down through a downlink (312) to stick locations (314), (316), (318), (320) and (322). Each of the sticks (314)-(322) is associated with a given locale (324), (326), (328), (330) and (332). The sticks are operable in a simulcast mode and also in a cellular mode. In the cellular mode, each of the sticks (314)-(322) is operable to receive a separate message that is distinct from the other cells. Pagers (36), having a known location at any of the locales (324)-(332) can then be selectively addressed and data transferred thereto. To prevent interference between adjacent RF locales, adjacent cells are not turned on during transmission to select cells in the cellular mode. These can be turned on at a different time. Orthogonal coding can be utilized such that adjacent cells can be turned on, thus increasing throughput.

Abstract: A digital mobile communications system which maintains synchronization among sending data of base stations, measures the time delay of radio waves from mobile stations under control at the control base station and instructs the value of time delay to each mobile station to adjust the timing of sending data of mobile stations to establish synchronization of communications between the base station and the mobile stations, wherein the system comprises means for measuring at mobile stations relative time delays of radio waves from at least one base station other than the control base station with respect to the radio waves from the control base station and periodically reporting the relative time delays to the control base station, and means for calculating at the base station the distances between the mobile station and the base stations and further determining the current geographic positions of the mobile station.

Abstract: In a direct sequence spread spectrum code division multiple access receiver using interference cancellation, the signal for cancellation is derived by demodulating the unwanted signals and re-modulating a carrier to create a near replica for subtraction from a delayed version of the total received signal. Errors in the demodulation process degrade the cancellation. The present invention provides an optimal way of using the reliability information in the demodulator decision variable either to turn the cancellor off for unreliable bit decisions or to partially disable the cancellor according to the bit reliabilities.

Abstract: A method for radiosynchronization of base stations in a simulcasting network which includes a plurality of base stations to be synchronized, comprising the following steps: a.) a first set of base stations transmitting respective synchronization signals; b.) a second set of base stations receiving at least one of the respective synchronization signals for the purpose of determining several estimates of synchronization error, where each of the several estimates is an estimate of synchronization error between one of the first set of transmitting base stations and one of the second set of receiving base stations; and, c.

Abstract: A method and system of communicating between moving participants such that each participant is provided with a first time slice and a respective priority listing containing the name of each participant once only, each participant thus having the top priority for one first time slice only. Also allocated to each participant is a second time slice during which he must transmit his identity as well as the identities of all his near neighbors within a radius R thereof. For each participant A there is stored the identity of all near neighbors B(A) and all far neighbors C(A) being within a radius R of his near neighbors B(A) and who are not also near neighbors B(A) of A. During each first time slice, any participant having a higher priority for the respective first time slice than all of his near and far neighbors may transmit data including the identities of at least those of his near neighbors who became near neighbors since his previous transmission.

Abstract: In a wireless telecommunications system (FIG. 1), over-the-air operations of a plurality of base stations (11 ) are synchronized via a synchronization signal that is embedded in the normal communications protocol that is used to convey traffic between a control switch (12) and the base stations. In the physical-layer protocol of the ISDN S or T basic-rate interface, the S or M bits are employed to conduct the synchronization signal. The synchronization signal is generated in the control switch and broadcast therein to port circuit packs (310) via a synchronization bit of a dedicated time-slot of a TDM bus (303).

Abstract: An information retrieval system and method for determining the location of a traveller based upon a comparison between broadcast radiowave frequencies at the location and a table of locations for radio stations which broadcast at those radiowave frequencies. By determining the location, the offset hour for the time zone where the radio station is located may be obtained for correctly displaying the hour on an analog watch. When the watch is moved to a different time zone, the hands are accelerated, forward or backward, until they indicate the local time. The location, such as a city, can also be displayed so that the traveller is apprised of both the correct time and present location automatically.

Abstract: A signal transmission system, for example a TDMA system, in which a carrier is divided into a plurality of traffic signal time slots, with optionally, some regularly interspersed control signal time slots. In order to be able to provide flexibility in the symbol rates and/or modulation schemes used by complementary users, the traffic signal time slots have one of at least two predetermined durations. However irrespective of the duration(s) of the traffic signal time slots, the number of symbols per traffic signal time slot remains substantially the same.

Abstract: In a radio paging system each pager includes a timer having a clock to provide date and time stamping of received messages. To set the time of the pager clock, the system base station transmits time message signals at regular intervals but which are of variable accuracy due to delays in signal formatting and propagation. The invention provides a pager wherein a control unit sets the timer clock in accordance with the time indicated by a transmitted time message signal which is determined to be the most accurate, such signal being selected as a time reference signal. The most accurate signal is determined by comparing the differences in indicated times of transmission and reception of an already selected current time reference signal with those of a presently received time message signal. If the presently received time message signal is the more accurate, it is substituted as a new time reference signal in place of the current time reference signal.

Abstract: A satellite (26) is operable to transmit timing information to a plurality of paging sites having towers (10) associated therewith and satellite receivers (48) associated therewith. This provides a simulcast transmission of the timing information such that the timing information arrives at each of the paging sites at substantially the same time. The data that is transmitted from a central station over a radio controlled link from an antenna (16) to a plurality of antennas (14) over a wireless communication link. Data is transmitted, due to the distances have a delay associated therewith. A synchronization network in the form a correlator (157) and a delay loop (158) provide for a delay between the data from the RCL (32) and the transmitted data from an antenna (12) to be adjusted such that the data transmitted from the paging transmitter (12) to the pagers (18) are transmitted from the paging transmitter antennas (12) at substantially the same time.

Abstract: A method and apparatus for use in a cellular mobile radio telephone system for initially setting a time alignment parameter in a mobile station. The method comprises the steps of estimating an optimal time alignment parameter for use during communication on a new traffic channel of a desired base station based on information available before the communication on the traffic channel is established, sending the estimated time alignment parameter to the mobile station, and setting the time alignment value in the mobile in accordance with the estimated time alignment parameter. An apparatus for initially setting a time alignment parameter is also provided according to a preferred embodiment.

Abstract: A telephone system in which communication between fixedly sited primary stations and transportable secondary stations is by way of respective time division duplex (TDD) radio links, particularly single frequency TDD links. In order to reduce radio interference between closely sited primary stations, their transmit periods are frame synchronized by using an externally produced radio signal. Conveniently a broadcast television field synchronization signal can be used.

Abstract: Disclosed is a radio paging receiver wherein changes from the synchronous state to the asynchronous state and vice versa of a radio receiver are detected, the period of time that the receiver is in the asynchronous state is measured by a timing means and recorded, and the recorded period of time is displayed.

Abstract: A method and apparatus are provided for synchronizing over-the-air time division duplexing communication within a defined geographical coverage area (201) of a communication system (200) that provides at least cordless radiotelephone operation between a plurality of portable radiotelephone transceivers and a plurality of telepoint base stations (202, 204, 206) geographically located within the coverage area (201). The communication system (200) transmits over-the-air a synchronization timing signal (203) including timing information corresponding to a transmit-and-receive duty cycle timing for time division duplexing communication. At least one telepoint base station (204, 206) within the coverage area (201) receives the synchronization timing signal (203). The at least one telepoint base station (204, 206) synchronizes its over-the-air time division duplexing communication transmit-and-receive duty cycle timing to the timing information.

Abstract: A method for re-establishing a communication link that has been lost between a portable unit (406) and a fixed unit or base station (402) provides for a way of quickly re-establishing the lost communication link, on the previously used RF channel. The method is begun by transmitting a link re-establishment code word (900) using MUX 1 after determining that synchronization has been lost (502) for a predetermined period of time (504). This is followed by automatically switching the portable unit (406) from MUX 1 to MUX 3 communication protocol. Followed by re-establishing communication (re-establish synchronization) between the portable (406) and base station (402) in MUX 3 and switching the two communication devices (402 and 406) back to MUX 1 after the communication link has been re-established. The same steps can be followed by base site (402) if it had been the first to detect loss of the communication link.

Abstract: A wireless communication system allow two-full two-way communication among a net or loop of stations. Each station is in direct communication with another member of the net such that a logical communication loop is created about the net. Each station combines its received signal with its own audio signal for retransmission to the next member of the loop whereby audio from said station is passed in turn to each of the other loop members. Transmission frequency hopping is utilized to insure system privacy and minimize interference with or from other loops operating in the same area. The system dynamically reconfigures itself to allow for the addition or dropping of a station without breakdown of the loop.

Abstract: A frequency modulated radio frequency broadcast network in which re-transmitting stations employ a synchronous frequency modulated booster system. Included in the frequency modulated booster system is a synchronous frequency .[.modualted.]. .Iadd.modulated .Iaddend.exciter for converting a frequency modulated intermediate frequency into a frequency modulated broadcast signal. The synchronous frequency modulated .[.exicter.]. .Iadd.exciter .Iaddend.includes phase locked loop circuits for synchronizing the re-transmitted frequency modulated broadcast signal with the frequency modulated intermediate frequency signal by detecting reference signals in the composite baseband of the intermediate frequency signal and in the composite signal frequency modulated broadcast signal.

Abstract: A frequency modulated ratio frequency broadcast network in which re-transmitting stations employ a synchronous frequency modulated booster system. Included in the frequency modulated booster system is a synchronous frequency modulated exciter for converting a frequency modulated intermediate frequency into a frequency modulated broadcast signal. The synchronous frequency modulated exciter includes phase locked loop circuits for synchronizing the re-transmitted frequency modulated broadcast signal with the frequency modulated intermediate frequency signal by detecting reference signals in the composite baseband of the intermediate frequency signal and in the composite signal frequency modulated broadcast signal.