Abstract: A switching network including both space division and time division switching stages where a permanent connection arrangement, interposed between the network input channels and a larger number of internal, time division channels at the input side of the space division stage, provides permanent rather than switched connections between each input channel and multiple internal channels. The pattern of permanent connections to multiple internal channels is designed such that the network is rearrangeable to avoid blocking to connect any idle output channel of the network to any busy or idle input channel.

Abstract: A switch path reservation arrangement where any paths that are established for calls between two switching modules are reserved such that most future calls between the two modules are set up promptly using previously reserved paths with a minimum of inter-module message communication. Relatively few calls require a path hunt involving inter-module negotiation to determine a new path. Such new path is not only assigned for the call but also thereafter reserved for calls between the two modules. Path reservations are changed only when required to avoid blocking a call. Thus, the path reservation arrangement adjusts the number of paths between modules on a per-call basis to dynamically match the call traffic load.

Abstract: A multi-channel communication security system where the information in an original information message is split among a number of channels in accordance with a message splitting routine such that the interception and analysis of any single channel does not compromise the privacy of the communication. The system provides secure communication terminal adapters in cojunction with user terminals for splitting and recombining of private communications together with control facilities in an integrated services digital network (ISDN) for selecting amoung a multiplicity of possible of message splitting routines and generating security code signals for transmission in separate D-channels to the user equipment.

Abstract: A tri-state optical device 400 is disclosed having photodiodes 401 and 402 with respective quantum-wells 403 and 404 in the intrinsic regions. The photodiodes are connected in series with a bipolar switch 406 and a source of electrical potential 405 for emitting a pair of optical output beams having various combinations of power levels depending on the state of the bipolar switch and the ratio of two optical control beams incident on the photodiodes. In one state of the tri-state device with the bipolar switch in a conducting state, the two output beams have complementary high and low power levels representing, for example, high and low logic levels "1" and "0". In a second state, the power levels of the two output beams are reversed, thus exhibiting complementary and symmetric output power levels.

Abstract: A distributed control switching system where calls, to and from a directory number that is shared by a key-system group of terminals, are processed cooperatiavely by multiple, distributed control units but in response to busy/idle data for the shared directory number stored advantageously by only a lead one of the control units. In addition to processing a call, for example to complete a connection to or from one of the terminals of the group, the multiple control units also cooperate as the call progresses to inform each of the group terminals of the call status as though the terminals were connected in parallel to a central office line as in an electromechanical key system.

Abstract: A method of discouraging the completion of certain classes of calls including wrong-number calls. Incoming calls from calling parties not included on a customer-specified screening list are first connected to an appropriate advisory announcement. Such calls are advantageously not extended to the customer station if the calling party disconnects within a specified time of receiving the announcement. To limit the delay of calling parties, the announcement is bypassed for callers included on the screening list and may be quickly interrupted by the transmission of a single, dual tone multifrequency digit from the calling station.

Abstract: A packet switch for switching packets received on a number of incoming packets channels to a number of outgoing packet channels. The packet switch includes a number of packet buffers each for storing packets received from an associated one of the incoming packet channels and further includes a number of selectors each permanently connected to each of the packet buffers and each associated with one of the outgoing packet channels for selectively connecting any of the packet buffers to the associated outgoing packet channel. A packet switch control mechanism responds to packets stored by the packet buffers by controlling the selective connections made by the selectors based on headers included in the stored packets. The control mechanism also responds to the stored packets by selectively effecting the transmission of the stored packets by the packet buffers.

Abstract: A multifilar transformer apparatus and winding method where first and second windings are bifilar wound around a core for NA turns, the first, second, third, and fourth windings are quadfilar wound around the core for NB turns, and the first and second windings are again bifilar wound around the core for NC turns. Winding symmetry is preserved and a turns ration of (NA+NB+NC):2NB is achieved.

Abstract: A packet flow control method where delay data are added into an initial packet as it traverses a packet switching network, and where the receiver of the initial packet, rather than the sender, establishes a window size based on such delay data to be used for the duration of a packet connection through the network. The delay data allow for the calculation of an average rather than an instantaneous network delay such that the flow control mechanism is not dependent on the magnitude of network congestion that happens to be present when the connection is first established. Since the receiver determines the window size, the flow control mechanism is put in place as an integral part of the initial packet exchange used to establish the two-way packet connection rather than requiring an additional packet communication to the receiver after a window size calculation by the sender.

Abstract: A virtual PBX capability is provided to a group of user packet stations served by a packet switching system. The system establishes a virtual circuit between each distinct pair of stations in the group. The stations exchange signaling packets via the virtual circuits and respond to such packets by coordinating the initiation and disconnection of voice, data, or image calls. All call processing, including the provision of features such as call forwarding and automatic callback, is accomplished by the stations without the aid of the switching system. A fraud prevention mechanism is included in the switching system to prevent unauthorized stations from communicating as part of the virtual PBX group.

Abstract: A switching system including a number of switching modules each having a plurality of access ports. Incoming and outgoing packet channels are extended between each switching module and an inter-module packet switch. Each switching module includes a packet switching unit that transmits user information packets, received from the access ports, via the incoming packet channel to the inter-module packet switch, and switches user information packets, received via the outgoing packet channel from the inter-module packet switch, to the access ports for inter-module packet-switched communication. The intermodule packet switch concurrently packet switches user information packets, received on a number of the incoming packet channels, via multiple independent paths to a number of the outgoing packet channels.

Abstract: A packet network test arrangement where a test packet is transmitted from a test source to a test destination via successive nodes of the packet network. Any node that fails to receive acknowledgement within a predetermined time of transmitting the test packet to a subsequent node responds by transmitting information to the test source concerning the failure and particularly defining the involved nodes. Accordingly, a single test can be used advantageously both to detect faults and to localize such faults between two network nodes. The test arrangement also provides for the loop-around of test packets received at the test destination thus enabling the test source to verify successful packet communications.

Abstract: A signaling arrangement where all terminal configuration data is stored in a switching system, but where each user terminal responds to a message from the system, defining one of the user terminal buttons as the selected call appearance at the terminal, by operating in a functional signaling mode to communicate with the system using functional messages concerning a call at the selected call appearance. Idle and ringing preference methods for use in terminating calls and auto-drop and auto-hold alternatives for use when moving from one call appearance to another are disclosed as well as methods for holding or dropping calls. Implicit and explicit conferencing methods are also disclosed.

Abstract: A call forwarding method that allows the called party to selectively forward individual alerting calls based, for example, on the calling party identity or on how busy the called party is at any given time, but without requiring the called party to first answer the calls. The called party can effect the transfer even though engaged in conversation with someone else.

Abstract: A fault recovery method for a distributed processing system where a message called a heartbeat is broadcast among the processors once during each major processing cycle. The heartbeat message indicates the physical and logical identity of the transmitting processor with respect to the system arrangement as well as the processor's present operational state. By monitoring the heartbeats from other processors, spare processors can autonomously take over the functions of failed processors without being required to consult or obtain the approval of an executive processor. The new physical location of a replaced processor will be automatically recorded by the other processors. The method has application to duplex standby and resource pool configurations as well as sparing arrangements.

Abstract: A multi-link interprocessor communication protocol that allows a pair of processors to increase the speed of their communication by using multiple physical links in parallel. When a message is sent from one processor to another, the message is packetized into smaller segments and loaded onto the available physical links according to a simple algorithm. The individual packets are received at the other end, their accurate transmission verified, and the received packets are then reassembled in the proper order. Packets of one or more messages to the same destination can go over the same physical link, or over different physical links; that is, there is no association of any message to any particular physical communication link. Packets received out of order on a per logical channel basis are stored until a correct sequence of packets is received after which their transmission to the message destination is effected.

Abstract: A distributed control switching system where the system control units cooperatively perform the terminating port determination function. Multi-port hunt groups having members that span a number of switching modules each having an associated control entity, are controlled in an efficient manner by assigning, for each multi-port hunt group, one of the switching modules as the group controller for that multi-port group. All calls to a given group necessarily require a control communication with the group controller which maintains the dynamic busy/idle data for the group and performs the hunting function to assign idle group members to calls.

Abstract: A distributed control switching system where multi-port hunt groups are controlled by hunting for idle group members in a sequential fashion starting with the members on one of the switching modules of the system and continuing through a predetermined sequence of modules until an idle group member is found. The busy/idle hunt data is distributed across the modules so that each module maintains the hunt data for only the group members on that module. Therefore, no inter-module control communication is devoted to updating the hunt data of other modules.

Abstract: A distributed control switching system having a plurality of switching modules interconnected by a time-multiplexed switch, where all call processing including the hunting of time-multiplexed switch paths between modules, is cooperatively performed by the switching modules without involving a system central control. To set up a given inter-module call, the terminating switching module sends a path hunt request message to the originating switching module defining the available time slots on the links from the originating switching module to the time-multiplexed switch. The originating switching module then selects a candidate set of time slots that are available on the links to the time-multiplexed switch from both the originating and terminating switching modules. Both the originating switching module and the terminating switching module are then available to process other path hunt requests while they contemporaneously negotiate to finally select the time slot to be used for the given call.

Abstract: A distributed control switching system where the system control units cooperatively perform the terminating port determination function. The control unit associated with the terminating port stores sequence call data defining whether calls are to be completed to that terminating port or are to be forwarded to another directory number. Upon determining that a given call is a sequence call, the control unit associated with the original terminating port determines the terminating port defined by the second directory number and effects a reduction of the sequence call to a simple call between the originating port and the second terminating port. This is done either by transmitting a control message defining the originating and terminating ports to the control unit associated with the second terminating port or by returning the setup sequence to the control unit associated with the originating port which then frees any switching system resources previously allocated to the call and transmits the control message.