Patent GB-1160546-A (GB)
Title: Selector Switching Systems Utilising Optical Interconnecting Paths Occupying a Common Space
Inventor: CATRAVAS SPIRO JOHN
IPC: H03K17/78
Filed: 1965-07-08
Abstract: 1,160,546. Signalling over light beams. S.J. CATRAVAS. Sept.30, 1966 [July 8, 1965], No.28971/65. Heading G1A. [Also in Division H4] In a selector switch, inter-connecting paths are established over positionable narrow light beams between common equipment (CLUI-CLUK), Fig. 1, which include beam originating and positioning arrangements, and fixed opto-electronic terminating units (SRUI-SRUN) which may each comprise a wide-angle retrodirective reflector. The common equipment comprises a number of common linking units the number provided being dependent on the desired grading and each being capable of being allotted to the establishment of any connection. The common equipment units, which are under a centralized control, each comprise two beam positioning sections, and are housed in a dark room. They may face the terminating units or be co-planar with them and facing a reflecting surface or surfaces. Each path comprises three sub-beams, namely intelligence conveying "send" and "return" beams, and an energizing beam for the send modulator. The source may comprise a laser, an electroluminescent source or a collection of sources, or a cathode ray tube, and linear polarization or pulsing may be introduced to prevent interference between the sub-beams at the termination units. A time-division cum distributer system is described in which a beam is modulated in different time slots by signals on different connections, and the beam is switched in position to different corresponding terminating units with each change of time slot. A four wire switching arrangement is involved. Numerous beam deflecting arrangements including one, two, or three lenses or mirrors are described with reference to Figs.3-15 (not shown), the movement being effected electromechanically, and the size of the moving optical elements being reduced to a minimum by the cutting away of parts of their area not required for beam transmission arrangements. Beam positioning in both a single line arrangement of terminating units and in a co-ordinate array is described. The use of a cathode ray tube is also suggested, and two pulse systems having a plurality of pulse supplies at different time intervals or having different amplitudes such that by a selection, a binary arrangement may be established in an averaging circuit connected in the tube deflecting circuit are described with reference to Fig. 17 (not shown). Electromagnetic optical element moving arrangements comprising a number of frames one within the other and separately movable between respective pairs of stops are described, one being a sliding ladder type of arrangement and another being an arrangement in which a smaller inner frame can be positioned in any one of the four corners of an outer bigger frame, the innermost frame carrying the optical element. A magnetic core arrangement in which an effective gap field can be transferred from between one pair of gaps to another for moving the above mechanisms is also described in detail. An analogue element moving arrangement in which the element is mounted on a member driven by a moving coil vibrator and the friction between the element and the member is electrically controllable in synchronism with the vibration is also described the mechanism being included in a servo-loop. Calibrating arrangements in which a number of accurately positioned transducer elements are positioned along two of the edges of a co-ordinate array of terminating units is described with reference to Figs. 29, 30 (not shown), a beam being set up separately on a predetermined pair of transducer elements along the two coordinates by means of a mirror, and an optical system and the mirror being swung away to allow the beam to fall on the selected terminating unit. Standby beam arrangements using semi-silvered mirrors are described, and a number of arrangements for splitting a single narrow beam or a single wide beam for use in a number of common units are exemplified. A plurality of narrow beams may be derived from a light source of small dimensions by a plurality of small aperture focusing elements of a comparatively large focal length compared with source size, arranged in the form of a honeycomb. The elements may be refractive or reflective. In order to maintain the illumination due to an oblique beam at the opto-electric termination units a plano-convex lens may be placed in intimate contact with a mirror. Telephone exchange systems using pulsed sources and polarization are described with respect to (Figs. 39, 40) respectively and in these arrangements provision is made in the common equipment to extract dialling pulses and to insert tone signalling.