International Business Machines Corporation

Donald C Flemming

Harold G Markey

Lynn P West

Ralph J Metz

Two systems of synchronous logic with dissimilar maximum clocking rate requirements use a single oscillating source to derive pseudo synchronous logic related clock signals having desired mutual properties. The periods of the clock T.sub.1 and T.sub.2 form the relationship ##EQU1## where S is a rational number and .alpha. is a largest denominator of T.sub.1 and T.sub.2. .alpha. then can be used to define a window that permits the transfer of data pulses from one of the systems to another without metastable conditions occurring in latch circuits.

Pseudo synchronous clocking

Digital exchange terminals are linked by earth satellite and terrestrial point-to-point time division trunks in a privately coordinatable time division switching and communication network serving to connectively link multiple ports attachable to separate voice telephone and data communication 'subscriber' trunk lines. The terminals operate relative to the satellite in a time division multiple access (TDMA) system with a portion of the system capacity (traffic burst channels) variably allocated to the terminals by demand assignment. The demand assignment is autonomously controlled by the terminals through supervisory communications carried over dedicated satellite channels (Order Wires) also utilized for synchronization. Internally the terminals employ modular multiplex switching between ports and 'virtual' channels (buffer stores) and voice activity compression (mapping of groups of up to n virtual channels into groups of up to m, m less than n, actual time division channels on the time division trunks). The activity compression serves to make the terrestrial and satellite channel resources of the system virtually available to more lines than can actually be served in one TDMA frame. External management (data processing) apparatus attached to a terminal line port supplies information stored by the terminals and used by the terminals to restrict options in selecting connection path segments between respective ports and virtual channels. Thus, the network system may be adapted on various levels to balance its traffic loads (demand assignment 'short term', network management/reconfiguration 'longer term', and physical relocation of terminal modules/ports 'longest term').

External management of satellite linked exchange network

Digital exchange terminals are linked by earth satellite in a privately coordinatable time division switching and communication network system serving multiple voice telephone and data communication lines. Terminals operate in each satellite time division frame to pass information switchably between variously paired lines and groups of n buffer stores, and between up to m (less than n) stores of each group (addressed in predetermined time order as internal time division channels termed virtual channels) and associated time-ordered groups of up to m external (satellite) channels. The selective switching between internal and external channels is termed activity compression handling. The external channels are adaptively appropriated to the terminals by demand assignment. Demand information exchanged between terminals at all network nodes is processed through a predetermined and pretimed reassignment computation process executed at all terminals. The terminals then exchange information representing proposed (bid) reassignments of external channels. In the absence of conflict the bid assignments are instituted. The activity compresssion acts as an intrinsic limiting factor on demand when more than m virtual channels are occupied.

Inter-related switching, activity compression and demand assignment

Modular digital exchanges linked by earth satellite provide coordinated time division switching and time compressed communication services relative to externally attached telephone and data (user) trunks. Branch exchange modules (NCU's) perform call switching, buffer storage, time compression and activity selective channel assignment handling between individual external user trunks and multi-bit channels of external time division highways (digital links). The latter are linked pyramidally to time division multiple access nodes of the satellite through Network (Nodal) Access Unit modules (NAU's) which perform further time compression handling and adaptive assignment of satellite channels based upon nodal distribution of demand. The NCU modules also provide 'local' switching between user trunks and 'tandem' linkage directly between NCU's (without NAU and satellite handling). The modules have individual common control processors which inter-communicate via reserved signaling channels on the digital links and satellite. The modularity is in increments suitable for adaptive deployment of connection equipment relative to satellite access nodes (e.g. to adapt to shifts in user populations and/or plant facilities).

Growing community of inventors

Rhinebeck, NY, United States of America

Donald C Flemming