GB2101828A - Exchange cabling - Google Patents

Abstract

In a complex electronic system, such as a telephone exchange, inter- rack cabling is a substantial part of the system's cost. To reduce this cabling, inter rack communication, at least in respect of information, uses beams of free space electro-magnetic radiation. In the present case infra-red beams are preferred because they are not very susceptible to external interference, and also do not cause much interference with other equipment. In some cases care is taken that the beams are directional, while in other cases such as the distribution of clock pulses some measure of non- directionality may be useful.

Description

SPECIFICATION Exchange cabling This invention relates to electronic data handling systems and especially to the arrangements for interconnecting the various units of such systems.

Complex electronic systems such as telephone exchanges and computer installations usually consist of separate equipment units such as racks or cabinets interconnected by multi-pair cables. Some of these cables convey electrical power, but others convey intelligence as low-power signals. The installation of such cables and their supporting structures is a significant portion of the cost and effort of installing the system, so the reduction of such cabling would be advantageous.

It is known to reduce the cabling by the use of multiplex techniques, either by time division multiplex, or by frequency division multiplex. Thus a number of independent channels can share a common wire or group of wires. The use of special cables such as coaxial cables or optical fibre cables can also enable a reduction in the cabling needed.

However these techniques still need physical connections to be made between units on site, plus supporting means to support the cabling.

An object of the invention is to reduce or even eliminate inter unit cabling in such systems.

According to the present invention there is provided an electronic data handling system, which includes a plurality of separate equipment units, wherein interconnections between said units are effected via beams of free-space electro-magnetic radiation.

Possible forms of rotation for the present purpose are radio, ultra-violet, visible light, or infra-red. At present the preferred radiation is infra-red, as it is less susceptible to interference from outside sources, and is also less liable to cause interference than other forms of radiation. In many cases the signal channels thus conveyed are multiplexed either in time division manner or in frequency division manner on each such link.

Embodiments of the invention will now be described with reference to the accompanying highly schematic drawings, in which: Figure 1 shows the application of the invention to closely-spaced equipment racks.

Figure 2 shows the application of the invention to separated equipment racks.

Figure 3 shows how the invention may be used with a row of equipment racks in a suite of racks.

Figure 4 shows the arrangement of a large number of links in parallel.

Figure 5shows the application of the invention to a system with non-adjacent racks.

In a simple case, Figure 1, connections are needed between adjacent racks or cabinets 1,2. This only needs the transmitting elements such as T1 and the receiving elements such as R1 to be mounted in corresponding positions on the two racks, and the sides of the cabinets have holes at these positions, as shown. If more than one link is needed, as is often the case when two-way information transfer is needed, baffles or screens which may be short tubes, are needed to separate the infra-red beams.

Focussing using lens systems can also be used.

The apertures can be sealed with a suitable glass or plastics material which is transparent to the light beams used, and may include or be lens for beam focussing. Such windows would be desirable to keep dust out.

In Figure 1 the transmitting infra-red source T1 is driven from a multiplexer MUX, while the receiving detector R1 feeds a demultiplexer.

Figure 2 shows in elevation and plan communication between the ends of adjacent suites of racks, which is similar to that between adjacent racks.

Hence the greater separation between the transmitter T2 and the receiver R2 cables for some control of the spread of radiation. As shown this uses short pipes such as 3,4 but collimating hoods can also be used. However, simple plastics lens, with or without reflectors, are also effective and are preferred. In general it is only necessary to confine the beam to within the width of the target rack, provided that the reflection from the rack surface is low. This can be ensured by giving the racks non-reflective outer surfaces, plus reflective inner surfaces near the infra-red sources and detectors.

Figure 3 shows how tubes, ducts, pipes or similar enclosed structures forming part of each rack can be so placed as to form a continuous run when the racks are installed with only short inter-rack gaps.

Hence we have one source T3, with two receiver detectors R3, R4 shown. The receiving pipes can have flared ends to reduce losses and interference, and to increase the permissible positioning tolerances. The inner surfaces of the tubes or the like have reflective or light scattering walls, and the remainder of the surfaces liable to receive light are non-reflective.

Where large numbers of links are needed, e.g. as between a distribution frame and the switching racks in a telephone exchange, Figure 4, the infra red sources TL1 - TL12 and detector RL1 - RL12 are positioned along the lengths of the frame and racks as shown. They have their beams parallel with beam widths shown to avoid interference by the use of directional devices such as hoods, lenses or reflectors. Alternate placing of transmitters and receivers, as shown, enables spacing to be closer without interference.

In the arrangement of Figure 4, as in other arrangements in which transmission is needed in opposite directions, protection against interference can be obtained by using different wavelengths in each direction, or different multiplexing methods.

In some cases such as the distribution of synchronising clock pulses, non-directional radiation may be used. Multiple reflections from various obstacles and walls may thus help to distribute the signals, but could cause distortion. Other connections between non-adjacent racks use elements on top of the racks with closed control of directivity using lenses or reflectors, see Figure 5. Hence we have lens such as 10 associated with radiation sources, and in some cases baffles such as 11 to shield a particular detector from a particular radiation source. Hence alignment of site, plus baffles such as 11,would be needed to block unwanted signals.

To protect against accidental interruption by blocking the direct paths of beams used as links, circuit or system techniques such as error checking, error connections, signal repetition, or physical redundancy or replication may be used. In addition, a light beam at a visible wavelength may be used to mark the position of an otherwise invisible communication beam. An automatic alarm may also be arranged to operate when a receiver fails to detect the correct radiation.

Claims (10)

1. An electronic data handling system, which includes a plurality of separate equipment units, wherein interconnections between said units are effected via beams of free-space electro-magnetic radiation.

2. A system as claimed in claim 1, and in which the radiation is infra-red.

3. A system as claimed in claim 1,and in which the radiation is ultra-violet.

4. A system as claimed in claim 2 or 3, and in which the or each said beam of infra-red or ultraviolet radiation is marked by a beam of visible light.

5. A system as claimed in claim 1, and in which the radiation is radio waves.

6. An automatictelecommunciation exchange, in which the equipment of the exchange is installed in a plurality of separate racks or cabinets, and in which interconnections between the racks or cabinets, at least for the conveyance of information appropriate to the communication connections to be set up is conveyed by beams of infra-red radiation.

7. An exchange as claimed in claim 6, and in which the beams are rendered directional by the use of lenses and/or reflectors.

8. An exchange as claimed in claim 6 or 7, and in which certain information such as clock pulses is conveyed in broadest fashion from a source to a plurality of receivers.

9. An exchange as claimed in claim 6, 7 or 8, and in which where several infra-red beams are in use, baffles are placed to shield some at least of the receivers from some at least of the sources.

10. An electronic data-handling system, substantially as described with reference to Figure 1, Figure 2, Figure 3, Figure 4, or Figure 5 of the accompanying drawings.