Abstract: A trunked radio frequency (RF) repeater system for public service trunking (PST) or the like includes a fault detection system having an RF output power monitoring, over-the-air RF monitoring and other repeater transceiver testing capabilities. An over-the-air monitor continually tests the digital signalling transmitted by different transceivers within the repeater system. The site controller automatically removes transceivers that test faulty, and does not permit tested faulty transceivers to go back on line until they have passed poll response, power output and RF digital signalling tests.

Abstract: An alternate home channel for a land mobile transmission trunked communication system designates one of a plurality of repeaters for a given site or coverage zone as an alternate home repeater. The control signals transmitted over the subaudio band for all home channels repeaters in that site are also duplicatively transmitted over the subaudio band of the alternate home repeater. Each mobile transceiver will be programmed with two channel numbers. One for the home repeater and the other for the site alternate home repeater. When the power is turned on, the mobile transceiver determines which repeater to monitor by scanning both the home and alternate home channels. When a valid control message is detected on either channel, that channel becomes the monitor channel. Operation of the mobile transceiver is then generally similar to prior operation, with the exception that the monitor channel (either home or alternate home channel) is used instead of just the home channel.

Abstract: A transmission line switching system includes transmission terminal matrix switches, reception terminal matrix switches and monitor circuits. Switching to and returning of the switching from any of the standby transmission lines are performed by connection of each of the matrix switches. An output from a control signal transmitter is connected to switching destination and switching returning destination transmission lines via the transmission matrix switch before the switching and returning of the switching, and control signals supplied through the transmission lines are received by a control signal receiver via the monitor circuit, thereby checking normality of the transmission lines.

Abstract: A switching system in a digital radio-communication system including a plurality of main radio-communication systems and a plurality of stand-by radio-communication systems provided for backing-up the main radio-communication systems. The switching system includes a plurality of switches independently operable from one another, the number of which is equal to the number of the stand-by radio-communication systems. Each switch switches between a stand-by radio-communication system defined in connection with the switch and a failed main radio-communication system, in a predetermined time.

Abstract: A system applicable to a digital radio communication system for switching a regular channel and a standby channel includes a demodulator associated with the standby channel. The demodulator has a phase locked loop for clock recovery the band width of which is variable. The band width of the phase lock loop is increased only when a channel switching operation is under way so as to guarantee clock synchronization.

Abstract: The radio transmitter-receiver system for increasing or decreasing communication channels comprises radio transmitter-receivers each including a separated intermediate frequency portion for modulation and demodulation and a separated microwave portion, and having a multiplexer and a divider therebetween. Local oscillators in the intermediate frequency portion have a variable frequency function and the operating frequency of the intermediate frequency portion can be easily changed. The intermediate frequency portions are connected to the microwave portions through the multiplexer or the divider and the frequency of the microwave to be communicated is easily changed. Thus, an increase or decrease of the communication channels is possible at a low cost.

Abstract: In a satellite communication system wherein a common channel is used for communication between a central station (10) and a plurality of remote stations (12) through a satellite transponder (11), in order to avoid system down due to fault of transmission of a broadcasting signal with a timing signal by the central station (10), the central station (10) comprises two portions (13, 14) positioned at different locations and a controller (15). When the first portion (13) detects fault of transmission of the broadcasting signal during the first portion (13) operates to communicate with the remote stations (12) under transmission of the broadcasting signal, the controller (15) is notified the fault and starts the second portion (14) in place of the first portion (13) so that the communication is maintained in the system without false. Those portions (13, 14) are assigned with ID numbers and can detect the fault by detecting operation of ID number.

Abstract: The signalling network has a main control unit which can communicate with any of a number of home units each associated with a separate household. Some home units have signal-repeater facilities. Each of the control units and the home units has an address identity unique in the network.When a signal is sent out targeted at a specific home unit, the main control unit monitors for acknowledgement of reaching its destination. If no such acknowledgement is received, the main control unit sends out the signal again, but re-routed via an intermediate home unit with a repeater facility.

Abstract: In a data communication system, such as an earth station for a satellite communication system, a level control unit enables control of an amplitude of a data signal which is reduced in a cable, regardless of the form of the data signal. The data communication system includes a first system including a unit for sending a continuous signal having a first frequency and a data signal having second frequency, a cable, and a second system for receiving both sent signals through the cable. The second system includes a unit for correcting an amplitude of the data signal on the basis of an amplitude of the continuous signal to a predetermined level. The second system may also include a unit for further correcting the amplitude of the data signal on the basis of the frequency difference between the data signal and continuous signal, so that the amplitude is adjusted at the second frequency.

Abstract: A radio frequency repeater system includes a independent error detection units which detect redundant and overlapping error conditions of the RF repeater stations. The error detection units notify the site controller and/or a system manager of the error conditions, and the failed repeater stations are removed from active service. The error detection units are then used to simulate actual service for the failed stations so that the stations can be placed back into service once they being operating properly again. Because the error detection units operate independently of the other components in the repeater system they can be used to trigger failure recovery mechanisms without becoming ineffective due to failure of other components.

Abstract: A method and apparatus for allowing a radio control console to failsoft to a predetermined channel assignment plan, without disrupting emergency calls then in progress, upon the failure of a CAD host computer link that would ordinarily provide control signals to the console. Channels are deassigned unless they are supporting an emergency call, and then reassigned to a default assignment. If the reassignment would cause a duplicate assignment, the duplicate assignment is first deassigned prior to making the new default assignment.

Abstract: A multichannel microwave relay station has first and second channels for respectively transmitting signals of different types of modulation, such as QAM and FM modulated signals. These different types of signal rely on a common standby transmission channel that is selectively capable of transmitting the different types of signals. The type of signal currently carried by the standby channel is automatically identified by a detector circuit, such as one that can automatically distinguish differences in the frequency spectrums of the different types of signals. A selecting circuit responds to the output of the detector circuit by selecting between first and second transmitting devices in the common channel, thereby dedicating it to the identified type of signal.

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.

Abstract: A power combiner includes an input power splitter driving a plurality (N) of amplifiers. The amplifier outputs have Z.sub.0 output impedance and are coupled by transmission (TX) lines of Z.sub.0 characteristic impedance to the junction point of a lossless power combiner. Short-circuiting switches located .lambda./4 from the junction power disconnect failed amplifiers from the combiner. According to the invention, a number M<N of the shorting switches are open during normal operation, so the impedance presented by the parallel TX lines at the junction of the combiner is Z.sub.0 /M. An impedance transformer associated with the combiner transforms the junction point impedance Z.sub.0 /M to Z.sub.0 at the combined output port, for example, by a .lambda./4 line having an impedance .sqroot.Z.sub.o.sup.2 /M.

Abstract: A channel switching system includes a synchronizing switch circuit including: two converters for monitoring input data signals respectively supplied through a regular channel and a stand-by channel, and when continuation of a predetermined number of bits having the same value is detected, outputting data signals for comparison in accordance with a predetermined rule; and a bit comparator for reading out the comparison data signals in response to a common clock signal, comparing bits of the data signals, sequentially changing the order of signal lines of either of the regular channel and the stand-by channel when a bit noncoincidence is detected, and supplying a control signal which instructs channel switching when a bit coincidence is detected.

Abstract: A radio relay method for digital communication using a heterodyne relay system consisting of terminal stations and relay stations each having radio repeaters using radio frequency of microwave or millimeter wave. The radio repeater usually receives a desired signal as a correct signal for a route to which the terminal and relay stations belong, however, the radio repeater can receive an undesired signal, whose level is beyond the threshold level of a squelch circuit in the radio repeater, produced by interference with an radio signal from an adjacent different route for example. When the desired signal decays due to fading for example and the undesired wave becomes dominant, the terminal station of the route must distinguish which relay station has a trouble.

Abstract: A communications system of the type having a normal operating system and a back-up standby system includes a branching circuit which supplies an output signal at a high power and at a lower power, respectively. The high power signal is supplied to the system which is presently operating as the normal operating system. Controlled switching means are provided to direct the high power signal to the back-up system when the back-up system is to operate as the normal operating system, and to couple the output of the back-up system to the communications system output upon this occurrence.

Abstract: In an optical transmission system, particularly a submerged system, a line finding system is provided which, in the event of a fault somewhere along the system, enables the remaining operative lines or paths to take over the traffic and thus "steer around" the fault. The laser sources of the submerged repeaters and switched by electrical selection at their input using failed clock or a supervisory signal to achieve the switching.

Abstract: The node of a point to multipoint data telecommunications system needs a receive clock to regenerate the data. The conventional method of regenerating the clock from received signals is difficult because there are gaps when no outstation is active. The invention reduces these problems by synchronizing the receive clock with the master send clock when there is no reception.

Abstract: A redundancy switching system which provides four reserve devices is disclosed which is suitable for use with from eight to twelve channels. The switches in the input switching network of this redundancy system are connected in first and second sections. Each section includes a ring of switches and two switches connected as appendages to the ring. Only as many switches are needed to control the input connection to the redundant devices as there are redundant devices. A similar number of switches are needed to control the output connection of the active devices.

Abstract: The invention comprises a method and a device for locating, isolating and by-passing a defective electrical device in an electrical circuit, and comprising sensing current and voltage at a first point in such circuit, on one side of such device, whereby the current and voltage are not significantly altered by the sensing process, sensing current and voltage at a second point in such circuit, on the other side of such device, whereby the current and voltage are not significantly altered by the sensing process, comparing such currents and voltages as between such two points, creating a control signal responsive to such compared currents and voltages, and, isolating such device from such circuit, and thereafter re-establishing such circuit whereby to by-pass such device, in response to a control signal of predetermined characteristics.

Abstract: An improved multipoint access data communication system with collision detection provides a duplicative communication medium, network interface units adapted for connection to transceivers on both media, transceivers adapted for connection to a plurality of network interface units, and a local collision detection circuit associated with each transceiver for detecting collisions between transmissions simultaneously attempted by two or more network interface units connected to the transceiver.

Abstract: A repeatered, multichannel fiber optic communication network includes a plurality of full duplex fiber optic channels and one or more auxiliary channels. In order to supervise and control the operation of the network, for both data transmission and fault/maintenance actions, each terminal station contains a processor-based subsystem capable of network monitoring, first level maintenance action, fault isolation, and remote network control and status reporting. This processor-based subsystem interfaces with each fiber optic channel, with an orderwire communication link, and with external input/output devices and surveillance equipment. Three substantially autonomous processor-based sections which are dedicated to performing specific functions within the overall network operation are employed for carrying out these separate interfacing tasks.

Abstract: A fail-safe CATV system center facility in which abnormalities in a normal down-data signal transmitter are automatically corrected for so that there is no loss of reception at the terminal units. FM and AM detectors detect the presence or absence of the normal FSK data signal. The outputs of the FM and AM detectors are AND'ed together then delayed to control the switch state of a switch which selects between the outputs of the normal down data signal transmitter and a back-up transmitter for coupling through to the cable system. The back-up transmitter produces a clock signal which is obtained by modulating a carrier signal having the same frequency as that of the normal down data signal, preferably a frequency shift keyed signal.

Abstract: An errorless line protection switching system utilizes a variable delay (29) in the spare channel (21-24, 26-29, 31-33) adjusted to provide data signal alignment with an impaired regular channel before substituting the spare channel for the regular channel. This switching system is able to provide bit error free channel substitution between the spare and any regular channel in a digital radio system by virtue of the data signal alignment capability. Data signal alignment is provided by first aligning clocking signals in fine incremental steps with each clocking signal derived from one of the two channels undergoing the substitution. Data signal alignment is then provided by shifting the spare channel in full bit positions until data alignment is indicated by a detector (119). Data signal alignment is also utilized to restore service to a regular channel so the spare channel may be removed from service.

Abstract: Transmission configurations are described for providing usable service despite the complete interruption of one or more of several transmission links. This is accomplished by encoding (11) the information content of each of a plurality of input signals (S.sub.1, S.sub.2 . . . S.sub.n) into a multiplicity of encoded signals (s.sub.1, s.sub.2 . . . s.sub.m) for simultaneous transmission along a multiplicity of transmission links (13.1, 13.2 . . . 13.m). At the receiver, a decoder (12) recovers the individual input signals. By accepting temporarily either a bandwidth or a signal-to-noise reduction, service is continued even though one or more of the transmission links fails.

Abstract: In an amplifier station for a trunk system, switching apparatus responsive to the absence or presence of a control signal selectively passes R. F. signals in a prescribed frequency band on a main transmission line to first and second lines. During normal operation of the amplifier relay coils are energized so as to engage second and third contacts for passing signals on the second line with amplification. When the amplifier is operating properly, PIN diodes short opposite ends of the first line for improving isolation in the station equipment. In the event of amplifier malfunction, first and third contacts are engaged thereby providing transmission along the first line. A tubular conductive member surrounds the switch contacts so as to provide capacitive coupling thereto. The tubular member is capacitively coupled to a ground plane to thereby by-pass signals which are above the desired passband of the trunk system.

Abstract: The efficient and secure operation of facilities such as roads, pipelines, etc., will increasingly require reliable and low cost means for distribution and collection of operational data along the facility. A method using simplex, party-line transmission of electromagnetic signals for distributing and collecting data packet messages is described which, in the case of random failures, automatically seeks out alternate routes. The system incorporates double and single end-of-message codes that cue the insertion of new messages, primary and secondary routes that are pre-determined by relative path losses and no-message timing signals, transmitted for phase locking and received signal level referencing purposes. The alternate routes are established by adjustable, enhanced antenna, or lens, side lobes. Alternate routing is triggered by an automatic gain control circuit. A preferred binary modulation, message format and station design are described.

Abstract: There is disclosed an optical transmission system which employs a plurality of receiver-transmitter pairs. One of the plurality of pairs is selected to propagate optical signals under control of switching means. The optical signal as propagated is monitored and if a fault is detected in the signal, another redundant receiver-transmitter pair is automatically switched in. This pair is also monitored to determine whether or not the optical signal is valid and if not, the sequence continues until a valid signal is being propagated.

Abstract: The present invention relates to a cooperating arrangement for a pair of space diversity stations (30 and 40) interconnected by a communication link (20) wherein each station normally communicates independently with a remote point (12) of the system while handling traffic related to a separate service region (32 and 42) or separate portion of an overall service region. At the occurrence of a fade condition at one of the two stations, the fading station alerts the other station of the pair of such condition, and both stations are enabled to cause the normal two-way communications between the faded station and the distant point to be routed over the communication link for two-way transmission between the non-faded station of the pair and the distant point along with the normal associated two-way transmissions between the non-faded station and the distant point.

Abstract: A method of counting transmission errors in a digital microwave link with a demand of commutation onto an emergency channel when the quality of the link becomes deficient, wherein the errors are counted during a period t which is always at least equal to a value t.sub.1 and at the most equal to a value t.sub.2, and which terminates when a fixed number N of errors has been detected, a pulse is stored upon each detection of N errors within a period t, and commutation is requested when n.sub.1 pulses have been stored consecutively.

Abstract: In a digital relay system, a standby channel is arranged to replace any one of five main channels. The standby channel contains a variable delay, and the data from the main channel to be replaced is passed along the standby channel prior to the changeover and is brought into synchronism with the data in the respective main channel by automatically controlling the length of the delay introduced by the variable delay arrangement, so that there is no slip or break in the data of the switched channel.