In a multiprocessor system comprising a plurality of individual processor modules interconnected by a bus structure, including a bus controller, for providing communication between the processor modules, a method and apparatus for interprocessor communication includes one of the processor modules sending a request signal to the bus controller to request a transmission; the bus controller polling the processor modules to identify the requesting processor module; the requestor processor module res...

A signal processing circuit utilizes a convolver correlating a reference carrier signal with a received signal. The correlator output is detected and then demodulated to output the signal information originally present on the carrier. For a conventional AM signal the reference carrier signal is applied at a frequency offset from the AM center frequency. When the carrier is an FM signal, the reference signal is applied at a frequency equal to the center frequency of the FM signal. Similar procedu...

In a communication network for communication between a plurality of nodes over a multi-channel communication medium 6, the network has a number of allocatable channels, . . . for data communication between nodes and a control channel 26 for allocating the allocatable channels to individual nodes. At least one of the channels operates under a token-passing protocol with a limited message packet length whereby selected messages may be sent between nodes with a predetermined maximum delay. The toke...

Personnel locating system for use in a facility having a plurality of rooms having doorways therein comprised of a plurality of portable transmitters. Each of the transmitters includes a battery and each generates an infrared signal. The system also comprises a plurality of fixed receivers positioned to cover different rooms at a facility. Each room has a receiver therein positioned to accept infrared radiation from a substantial portion of the volume of the room. Each receiver is capable of sen...

This invention is intended for the communication between a first communication device (e.g., an IC card) and a second communication device (e.g., a card terminal) by preventing the faking of the IC card or card terminal, for example, thereby allowing correct information exchange between them. The invention provides the IC card with a first encryption means and the card terminal with a second encryption means. In consequence, communication signals in both directions are encrypted, and random numb...

A communication interface for the protocol of a layer 1 using an ISDN digital communication network, includes: a first communication controller to execute the communication control for a standard terminal; a second communication controller to execute the communications control for a network terminal device; and a switch between to switch the first and second communication controllers. The first communication controller executes the control as a layer 1 of the ISDN standard terminal. The second c...

In a spread spectrum communication system, sequence signals are developed in both a transmitter and receiver, in each case being derived from a clock signal through digital count-down and logic circuitry including a programmable counter which receives control number defining groups of signals from a memory under control of an indexing counter. A sequence signal in the transmitter is applied through a filter to produce a filtered signal which is propagated as a sequence of variations of alternati...

A communication system comprising a plurality of devices interconnected into a loop and each provided with two pairs of sending and receiving terminals for transmitting signals in directions different from each other. Each of the devices is connected to the other devices immediately adjacent thereto on the loop by a pair of transmission channels connected to the two pairs of sending and receiving terminals and each including a sending line and a receiving line. Each device comprises a first arri...

An audio signal and a selected one of a plurality of sub-audio tones are transmitted to a plurality of receiving each being capable of being conditioned by first, second or third selected sub-audio tones so that either all receivers, or only a select group of all of the receivers or only an intended group are the receivers accept the transmitted audio signal, there being as many selectable second sub-audio signals as there are groups and as many selectable third sub-audio signals as there are re...

Messages are transmitted via a gateway between terminal equipments in different communication networks. The message includes a source address, a destination address, a first header information set, at least one data block, and an end code. The source address corresponds to the terminal equipment or the gateway from which the message is transmitted. The destination address corresponds to the terminal equipment or the gateway to which the message is directed. The first header information set has r...