AU7014898A - Cable system - Google Patents

Description

WO 98/48487 PCT/AU98/00289 Cable system Introduction The present invention relates generally to communications systems, and in particular the invention provides an improved connection protocol for 5 the interconnection of components in a communications system. Background Typically in communications systems, many of the faults that occur through the life of the system arise out of cabling and connector problems. These problems are generally greater following initial installation of a system 10 but also occur periodically during the life of the systems. The problems exhibited fall into two categories: 1) component or conductor failure; 2) wiring errors. The present invention provides a method of reducing the second of 15 those sources of problems by reducing the number of wiring errors and also increasing the systems tolerance to some types of wiring errors. Summary of the Invention According to a first aspect, the present invention provides a communications connection protocol for connecting two units of a 20 communication systems thereby enabling communication between the units in at least one direction, the protocol being characterised in that: at least one signal is communicated between the units; each signal is produced by a balanced transmitter in one unit; each signal is communicated over a pair of conductors as a balanced 25 signal from the transmitter to a balanced receiver in the other unit; the electrical connection between the transmitter and receiver passes through a connector as it exits the one unit passes via a cable and through a second connector as it enters the other unit; the cable is configured as a plurality of conductors in a flat non 30 crossing arrangement such that the order of the conductors is fixed and constant over the length of the cable; and the pairs of conductors allocated to each balanced signal are symmetrically located in the cable and connectors. According to a second aspect the present invention provides a 35 communication unit arranged to be connected to a communication system using the above protocol.

WO 98/48487 PCT/AU98/00289 2 In one configuration the cable also carries power, in which case two power conductors are also symmetrically placed in the cable. Earth conductors if present are either located: a) centrally in the case of a cable having an odd number of conductors; 5 or b) as a symmetrical pair in a cable having an even number of conductors. Cables can have any number of conductors from 2 up but preferred configurations have 4, 5, 6, 7, 8, 9 or 10 conductors. 10 Preferably the electrical protocol of the balanced signals will be in accordance with the RS422 standard. Brief Description of the Drawings Embodiments of the invention will now be described in greater detail with reference to the following drawings in which: 15 Figure 1 schematically illustrates an example of the connection protocol between two units in a system; Figure 2 schematically illustrates an example of a dropper method of connecting units; Figure 3 schematically illustrates an example of a chaining method of 20 connecting multiple units; and Figures 4, 5 & 6 show examples of different cable configurations and signal allocations. Detailed Description of Embodiments Referring to Figure 1 an embodiment of the invention is illustrated in 25 which a first network unit 11 communicates with a second network unit 12 via a communication cable 13. Although communication between the first unit 11 and the second unit 12 of the illustrated embodiment is bi directional, the first unit 11 will be referred to as the sending unit and the second unit 12 will be referred to as the receiving unit. 30 In the sending unit 11, a balanced transmitter 21 generates a pair of balanced signals on lines 31, 32 using polarity insensitive modulation for transmission of information to the receiving unit 12 where the balanced signals passing through lines 41, 42 are received by a receiver 51. Between the sending unit 11 and the receiving unit 12 the balanced 35 signals from the transmitter 21 pass through the third and sixth cores of an eight way flat cable 13.

WO 98/48487 PCT/AU98/00289 3 In the illustrated embodiment signals in the reverse direction from the receiving unit 12 to the sending unit 11 are generated as a balanced pair by transmitter 52 and pass through lines 43, 44, cores 2 and 7 of cable 13 and lines 23, 24 in the sending unit 11 to the receiver 22. 5 Power is also passed from one communications unit to the next in the illustrated embodiment, including a reference earth passing through cores 4 and 5 of the eight way cable 13 and a balanced ac supply passing through the cores 1 and 8. Circuitry in each unit 11, 12 is powered from the balanced ac supply 35, 36, 45, 46 via bridge rectification 23, 53 and suitable filtration and 10 regulation as necessary. Referring to Figure 2, a number of system units are illustrated connected in parallel via a main distribution cable 63 and a series of dropper cables 64 connected between the distribution cable 63 and respective units 11, 12. In this case, a plurality of 'T' connectors 65 are provided along the 15 length of the main distribution cable 63 and the dropper cables 64 connect into these 'T' connectors with their other ends connected to connector 54 of the respective units 11, 12. The orientation of cables 63 and 64 will not affect the operation of the communication system as is illustrated in the case of units 11 & 12 of Figure 2, which respectively are connected by a twisted 20 and an untwisted dropper cable. In an alternative arrangement illustrated in Figure 3, a loop topology system is shown in which a number of units are daisy chained together, in which case each communication unit 11, 12 will be both a sending unit for the next unit in the chain and a receiving for the previous unit in the chain. 25 Hence in Figure 3 the communication unit 11, is shown to include a transmitter 21 and receiver 22 of its sending section communicating with the next chained unit and receiver 51 and transmitter 52 of its receiving section communicating with the previous chained unit. Switches 24, 25 operate in unison in the event of unit failure in order 30 to isolate the unit and bypass it so that units further up or down the chain may continue to receive communications originating on the opposite side of the damaged unit. Returning to Figure 1, the flat cable 13 is terminated at either end by connector plugs 14 and 15 of the type designed to crimp over a flat cable 35 such that the pins of the connector are ordered identically with the cable WO 98/48487 PCT/AU98/00289 4 cores in respect to the signals they carry. The cable connector plugs are respectively removably received in corresponding connector sockets 24, 54. The inter-connecting cable 13 and its respective connector plugs 14, 15 are symmetrical such that the cable can be reversed (i.e. its ends swapped) 5 and rotated (i.e. the connectors rotated through 1800). Further, because all power and signal conductors in the cable are symmetrically ordered in the electrical protocol chosen, one end of the cable cari be rotated relative to the other without affecting the function of the communications between units 11, 12. This is illustrated in Figure 2 in which the cable 13 is twisted 10 between unit 11 and unit 12. The signal protocol employed in this embodiment is a non-return to zero protocol in which logical zeros are represented by a signal transition and logical ones are represented by a steady state signal such that the signals transmitted through cable 13 are polarity insensitive. It is immaterial 15 whether the balanced pair from a transmitter is connected to its respective receiver in phase or out of phase, because levels are not directly representative of logical states. In the case of the embodiment of Figures 1, 2 and 3 an eight-way cable carries two pairs of signals in four cores plus two reference earth cores and a 20 balanced ac supply on the remaining 2 cores. However it is not essential that a cable carry bi-directional signals, nor is it essential that the cable carry power. Some alternative cable configurations are illustrated in Figures 4, 5 and 6. Figure 4 illustrates 4, 5, and 6 core cables with the configurations listed 25 below. In the examples of Figures 4a and 4b in particular, the respective configurations are mirror images of one another and illustrate the symmetry of the protocol of the present invention. Figure 4(a) illustrates a Four Core Cable with the following configuration: 30 Core 1 - Signal al Core 2 - Signal bi Core 3 - Signal b2 Core 4 - Signal a2 WO 98/48487 PCT/AU98/00289 5 Figure 4(b) illustrates a Four Core Cable with the following configuration: Core 1 - Signal a2 Core 2 - Signal b2 Core 3 - Signal bi 5 Core 4 - Signal al Figure 4(c) illustrates a Five Core Gable with the following configuration: Core 1 - Signal at Core 2 - Signal bi 10 Core 3 - Earth Core 4 - Signal b2 Core 5 - Signal a2 Figure 4(d)Five illustrates a Core Gable with the following configuration: 15 Core 1 - Signal at Core 2 - Signal bl Core 3 - Neutral Core 4 - Signal b2 Core 5 - Signal a2 20 Figure 4(e) illustrates a Six Core Cable with the following configuration: Core 1 - ac or dc power Core 2 - Signal al Core 3 - Signal bi 25 Core 4 - Signal b2 Core 5 - Signal a2 Core 6 - ac or dc power Figure 4(f) illustrates a Six Core Cable with the following configuration: 30 Core 1 - Drain (for earth or induced V sensor) Core 2 - Signal at Core 3 - Signal bi Core 4 - Signal b2 Core 5 - Signal a2 35 Core 6 - Drain (for earth or induced V sensor) WO 98/48487 PCT/AU98/00289 6 Figure 5 illustrates the further cable configurations listed below: Figure 5(a) illustrates a Seven Core Cable with the following configuration: Core 1 - ac or dc power, voltage sensor or earth 5 Core 2 - Signal al Core 3 - Signal bi Core 4 - Power earth Core 5 - Signal b2 Core 6 - Signal a2 10 Core 7 - ac or dc power, voltage sensor or earth Figure 5(b) illustrates a Seven Core Cable with the following configuration: Core 1 - Signal al Core 2 - Signal bi 15 Core 3 - Signal cl Core 4 - Signal earth Core 5 - Signal c2 Core 6 - Signal b2 Core 7 - Signal a2 20 Figure 5(c) illustrates a Eight Core Cable with the following configuration: Core 1 - Signal at Core 2 - Signal bi Core 3 - Signal cl 25 Core 4 - Signal dl Core 5 - Signal d2 Core 6 - Signal c2 Core 7 - Signal b2 Core 8 - Signal a2 WO 98/48487 PCT/AU98/00289 7 Figure 5(d) illustrates a Ten Core Cable with the following configuration: Core 1 - ac or dc power, c voltage sensor, or earth Core 2 - Signal al Core 3 - Signal bi 5 Core 4 - Signal cl Core 5 - Signal dl Core 6 - Signal d2 Core 7 - Signal c2 Core 8 - Signal b2 10 Core 9 - Signal a2 Core 10 - ac or dc power, c voltage sensor, or earth Finally a further 10 cone cable configuration, is illustrated in Figure 6 having the following configuration: 15 Core 1 - Signal al Core 2 - Signal bi Core 3 - Signal cl Core 4 - Signal dl Core 5 - ac or dc power, voltage sensor or Earth 20 Core 6 - ac or dc power, voltage sensor or Earth Core 7 - Signal d2 Core 8 - Signal c2 Core 9 - Signal b2 Core 10 - Signal a2 25 It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (15)

1. A communications connection protocol for connecting two units of a communication systems thereby enabling communication between the units in at least one direction, the protocol being characterised in that: 5 at least one signal is communicated between the units; each signal is produced by a balanced transmitter in one unit; each signal is communicated over a pair of conductors as a balanced signal from the transmitter to a balanced receiver in the other unit; the electrical connection between the transmitter and receiver passes 10 through a connector as it exits the one unit, passes via a cable and through a second connector as it enters the other unit; the cable is configured as a plurality of conductors in a flat non crossing arrangement such that the order of the conductors is fixed and constant over the length of the cable; and 15 the pairs of conductors allocated to each balanced signal are symmetrically located in the cable and connectors.

2. The communications connection protocol as claimed in claim 1, wherein the cable also carries power, and two power conductors are also symmetrically placed in the cable. 20

3. The communications connection protocol of claim 1 or 2, wherein the cable has an odd number of conductors and a centrally located conductor is an earth conductor.

4. The communications connection protocol of claim 1, 2 or 3, wherein the cable includes a pair of earth conductors symmetrically located in the 25 cable.

5. The communications connection protocol as claimed in any one of claims 1 to 4, wherein the balanced signals are in accordance with the RS422 standard.

6. The communications connection protocol as claimed in any one of 30 claims 1 to 5, wherein the cable has either 2, 4, 5, 6, 7, 8, 9 or 10 conductors.

7. The communications connection protocol as claimed in any one of claims 1 to 6, wherein signals transmitted over the cable are modulated using a polarity insensitive modulation technique.

8. A communication unit arranged to be connected to a communication 35 system employing a communications connection protocol for connecting adjacent units of the system thereby enabling communication between the WO 98/48487 PCT/AU98/00289 9 units in at least one direction, the communications unit including a balanced transmitter having two balanced serial output lines and an output port having a symetrical connector arranged to receive a mating ribbon cable connector, the two output signal lines being located symetrically in the 5 output port connector and the protocol being characterised in that: at least one signal is communicated from the transmitter in the communications unit to a receiver in an adjacent unit; each signal is produced by a balanced transmitter in one unit; each signal is communicated over a pair of conductors as a balanced 10 signal from the transmitter to a balanced receiver in the other unit; the electrical connection between the transmitter and receiver passes through the symetrical connector as it exits communications one unit passes via the ribbon cable and through a second connector as it enters the adjacent unit; 15 the cable is configured as a plurality of conductors in a flat non crossing arrangement such that the order of the conductors is fixed and constant over the length of the cable; and the pairs of conductors allocated to each balanced signal are symmetrically located in the cable and connectors. 20

9. A communication unit arranged to be connected to a communication system employing a communications connection protocol for connecting adjacent units of the system thereby enabling communication between the units in at least one direction, the communications unit including a balanced receiver having two balanced serial input lines and an output port 25 having a symetrical connector arranged to receive a mating ribbon cable connector, the two output signal lines being located symetrically in the output port connector and the protocol being characterised in that: at least one signal is communicated to a receiver in the communications unit from a transmitter in an adjacent unit; 30 each signal is produced by a balanced transmitter in one unit; each signal is communicated over a pair of conductors as a balanced signal from the transmitter to a balanced receiver in the other unit; the electrical connection between the transmitter and receiver passes through the symetrical connector as it exits communications one unit passes 35 via the ribbon cable and through a second connector as it enters the adjacent unit; WO 98/48487 PCT/AU98/00289 10 the cable is configured as a plurality of conductors in a flat non crossing arrangement such that the order of the conductors is fixed and constant over the length of the cable; and the pairs of conductors allocated to each balanced signal are 5 symmetrically located in the cable and connectors.

10. The communications unit as claimed in claim 8 or 9, wherein the cable also carries power, and two power conductors are also symmetrically placed in the cable.

11. The communications unitof claim 8 9 or 10, wherein the cable has an 10 odd number of conductors and a centrally located conductor is an earth conductor.

12. The communications unitof claim 8, 9, 10 or 11, wherein the cable includes a pair of earth conductors symmetrically located in the cable.

13. The communications unitas claimed in any one of claims 8 to 12, 15 wherein the balanced signals are in accordance with the RS422 standard.

14. The communications unitas claimed in any one of claims 8 to 13, wherein the cable has either 2, 4, 5, 6, 7, 8, 9 or 10 conductors.

15. The communications unitas claimed in any one of claims 8 to 14, wherein signals transmitted over the cable are modulated using a polarity 20 insensitive modulation technique.