Local area network

• US 4,674,085 A
• Filed: 10/06/1986
• Issued: 06/16/1987
• Est. Priority Date: 03/21/1985
• Status: Expired due to Term

• Current Assignee: NCR Corporation
• Original Assignee: American Telephone & Telegraph Company (AT&T, Inc.), AT&T Information Systems Inc. (AT&T, Inc.)
• Inventors: Aranguren, William L., Sidey, Michael J., Restrepo, Mario A.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Scutch, III, Frank M.
• Application Number:
  US06/815,959
• Time in Patent Office: 253 Days
• Field of Search: 370/60, 370/94, 370/85, 370/86, 370/15, 340/825.5, 340/825.05
• US Class Current: 370/408
• CPC Class Codes: H04L 12/44 Star or tree networks

Abstract

A modular, hierarchical local area network is realizable by using existing twisted pair wiring, for example, in a building together with several elements known as network access units and hub units. A network access unit is connected to a device (microprocessor, display terminal, peripheral device, other local area network, information systems network or the like) in the local area network to give that device access to and from the network. The network access device is designed for simple daisy chaining with other devices to form a node when devices are colocated in the same section or room in the building. The hub unit is the network building block which permits extensive expansion of the local area network. It provides a connection point for access units or other hub units, performs collision detection operations, if necessary, and serves as a loop-back point for the network. Switchably connectable termination impedances and loop-backs are automatically passed to the appropriate points in the local area network. While most small local area networks are considered for intra-building applications, the present network is applicable to inter-building applications, also.

Claims

1. A local area network arrangement for providing communications on first and second segmented transmission means among a plurality of devices, each device communicating through a network access means connected to the device and to the first and second segmented transmission means, each network access means including,

transceiver means for translating signals from the device to the first segmented transmission means via first and second ports and for translating signals from the second segmented transmission means via first and second ports to the device,

the first port including input terminal means for connecting the first segmented transmission means thereto, output terminal means for connecting the second segmented transmission means thereto, and means for terminating the first and second segmented transmission means each with a characteristic termination impedance, the terminating means being connected from the input terminal means of the first port to the output terminal means of the first port only in the absence of connection between the segmented transmission means and the first port, and

the second port including input terminal means for connecting the second segmented transmission means thereto, output terminal means for connecting the first segmented transmission means thereto, and loop back means connected from the input terminal means to the output terminal means of the second port for providing a low impedance electrical path therebetween only in the absence of a connection between the segmented transmission means and the second port,

the input and output terminal means of the first port being connected directly to the output and input terminal means, respectively, of the second port, the second port of each network access means adapted for connection via the segmented transmission means to the first port of an adjacent network access means.

2. The local area network arrangement as defined in claim 1 wherein the first segmented transmission means is a twisted pair of wires and the second segmented transmission means is a twisted pair of wires.

3. The local area network arrangement as defined in claim 1 wherein the local area network is further comprised of at least first hub means for expanding the local area network by providing interconnectivity between other such hub means and network access means via first and second segmented transmission means, the at least first hub means including,

first and second common bus means,

first through K-th ports, each port having both input terminal means for connecting the first segmented transmission means thereto and output terminal means for connecting the second segmented transmission means thereto,

first through K-th port circuit means, each port circuit means being connected to the corresponding port for translating signals from the input terminal means to the first common bus means and for translating signals from the second common bus means to the output terminal means,

an access means connected in circuit relationship to the first and second common bus means for translating signals from the first common bus means to the first segmented transmission means and for translating signals from the second segmented transmission means to the second common bus means, and

a (K+1)th port including input terminal means for connecting the second segmented transmission means thereto, output terminal means for connecting the first segmented transmission means thereto, and loop back means connected from the input terminal means to the output terminal means of the (K+1)th port for providing a low impedance electrical path therebetween only in the absence of a connection between the segmented transmission means and the (K+1)th port.

4. The local area network arrangement as defined in claim 3 wherein the first segmented transmission means is a twisted pair of wires and the second segmented transmission means is a twisted pair of wires.

5. The local area network arrangement as defined in claim 3 wherein the at least first hub means further includes collision detection means connected to the first common bus means and the access means for determining the occurrence of a collision between two or more signals on the first common bus means and supplying a collision signal representing such collision occurrence to the access means and, in the absence of signal collision, for permitting transmission of the signal on the first common bus means to the access means.

6. The local area network arrangement as defined in claim 5 wherein the first segmented transmission means is a twisted pair of wires and the second segmented transmission means is a twisted pair of wires.

7. The local area network arrangement as defined in claim 5 wherein the collision detection means is connected in the circuit between the first common bus means and the access means.

8. The local area network arrangement as defined in claim 7 wherein the first segmented transmission means is a twisted pair of wires and the second segmented transmission means is a twisted pair of wires.

9. The local area network arrangement as defined in claim 8 wherein the collision detection means, upon detection of signal collision on the first common bus means, inhibits transmission of colliding signals to the access means.

10. The local area network arrangement as defined in claim 5 wherein the first common bus means is a K-input logic element capable of performing a logical OR function on the signals from first through K-th port circuit means.

11. The local area network arrangement as defined in claim 10 wherein the first segmented transmission means is a twisted pair of wires and the second segmented transmission means is a twisted pair of wires.

12. A network access arrangement for use in a local area network providing communications on first and second segmented transmission means among a plurality of devices, each device connected through a corresponding network access arrangement connected to the device and to the first and second transmission means, said network access arrangement including,

transceiver means for translating signals from the device to the first segmented transmission means via first and second ports and for translating signals from the second segmented transmission means via first and second ports to the device,

the first port including input terminal means for connecting the first segmented transmission means thereto, output terminal means for connecting the second segmented transmission means thereto, and means for terminating the first and second segmented transmission means each with a characteristic termination impedance, the terminating means being connected from the input terminal means of the first port to the output terminal means of the first port only in the absence of connection between the segmented transmission means and the first port, and

the second port including input terminal means for connecting the second segmented transmission means thereto, output terminal means for connecting the first segmented transmission means thereto, and loop back means connected from the input terminal means to the output terminal means of the second port for providing a low impedance electrical path therebetween only in the absence of a connection between the segmented transmission means and the second port,

the input and output terminal means of the first port being connected directly to the output and input terminal means, respectively, of the second port, the second port of each network access arrangement adapted for connection via the segmented transmission means to the first port of an adjacent network access arrangement.

13. The network access arrangement as defined in claim 12 wherein the first segmented transmission means is comprised of a twisted pair of wires and the second segmented transmission means is comprised of a twisted pair of wires.

14. A hub arrangement for use in a local area network providing communications on first and second segmented transmission means among a plurality of devices, each device connected through a corresponding network access arrangement connected to the device and to the first and second transmission means, the local area network further comprised of at least one of said hub means, said hub means providing an expansion capability to the local area network by providing interconnectivity between other such hub means and network access means via first and second segmented transmission means, said hub means including,

first and second common bus means,

first through K-th ports, each port having both input terminal means for connecting the first segmented transmission means thereto and output terminal means for connecting the second segmented transmission means thereto,

first through K-th port circuit means, each port circuit means being connected to the corresponding port for translating signals from the input terminal means to the first common bus means and for translating signals from the second common bus means to the output terminal means,

an access means connected in circuit relationship to the first and second common bus means for translating signals from the first common bus means to the first segmented transmission means and for translating signals from the second segmented transmission means to the second common bus means, and

a (K+1)th port including input terminal means for connecting the second segmented transmission means thereto, output terminal means for connecting the first segmented transmission means thereto, and loop back means connected from the input terminal means to the output terminal means of the (K+1)th port for providing a low impedance electrical path therebetween only in the absence of a connection between the segmented transmission means and the (K+1)th port.

15. The hub arrangement as defined in claim 14 wherein the first segmented transmission means is comprised of a twisted pair of wires and the second segmented transmission means is comprised of a twisted pair of wires.

16. The hub arrangement as defined in claim 14 wherein the at least first hub means further includes collision detection means connected to the first common bus means and the access means for determining the occurrence of a collision between two or more signals on the first common bus means and supplying a collision signal representing such collision occurrence to the access means and, in the absence of signal collision, for permitting transmission of the signal on the first common bus means to the access means.

17. The hub arrangement as defined in claim 16 wherein the first segmented transmission means is comprised of a twisted pair of wires and the second segmented transmission means is comprised of a twisted pair of wires.

18. The hub arrangement as defined in claim 16 wherein the collision detection means is connected in the circuit between the first common bus means and the access means.

19. The hub arrangement as defined in claim 18 wherein the first segmented transmission means iscomprised of a twisted pair of wires and the second segmented transmission means is comprised of a twisted pair of wires.

20. The hub arrangement as defined in claim 19 wherein the collision detection means, upon detection of signal collision on the first common bus means, inhibits transmission of colliding signals to the access means.

21. The hub arrangement as defined in claim 16 wherein the first common bus means is comprised of a K-input logic element capable of performing a logical OR function on the signals from first through K-th port circuit means.

22. The hub arrangement as defined in claim 21 wherein the first segmented transmission means is comprised of a twisted pair of wires and the second segmented transmission means is comprised of a twisted pair of wires.