At&t Information Systems Inc.

American Telephone and Telegraph Company and At&t Information Systems

At&t Company

Lloyd A Hasley

Jaan Raamot

Andrew D Franklin

James E Smith

A packet switching system is disclosed for transmitting variable length packets between system ports. Each byte of each packet has a special one-bit field for indicating whether the byte is the last byte of a packet. A '1' in this field specifies that the byte is the last byte of a packet and activates port control circuitry that changes the potential on a system control conductor to indicate that the system data bus is now idle and free for use by other ports.

Variable length packet switching system

A clock recovery circuit for recovering the clock from an incoming data stream. The circuit comprises a transition detector and a module 3 counter operating at three times the expected rate of the incoming clock. A clock pulse is generated by the counter one count interval after a transition is detected.

Clock recovery circuit

A packet switching system having separate arbitration and data buses together with circuitry for dividing the buses into a plurality of time segments termed phases. The plurality of phases permit a like plurality of separate arbitration operations and a like plurality of separate data exchanges to be effected concurrently on the arbitration bus and data bus, respectively. The use of n phases increases the data transmission capability of the system by a factor of n over prior art arrangements using only a single phase.

Multiphase packet switching system

A distributed packet switching system in which a centralized switch is not used and, instead, each transmitting port contains the intelligence required to derive and then insert the destination port and station addresses into the header of each packet to be transmitted by the port. The port circuitry that derives the destination addresses operates under control of a central controller which, prior to the setup of each call, receives information identifying the transmitting port and calling station as well as the destination station number dialed at the calling station. The controller processes this data to derive the destination port and station addresses. The derived addresses are sent to and stored in a RAM in the transmitting port. The RAM outputs the destination port and station addresses for each packet subsequently transmitted by the port on the call.

Growing community of inventors

Carrollton, TX, United States of America

Lloyd A Hasley