GB604030A - Improvements in photo-electric telegraph transmitters - Google Patents

Abstract

604,030. Automatic control systems. TELETYPE CORPORATION. Nov. 21, 1945, No. 31357. Convention date, June 15, 1944. [Class 38 (iv)] [Also in Group XL (b)] In a photo-electric telegraph transmitter, message-tape feeding mechanism and scanning mechanism therefor are automatically maintained in phase as a result of scanning control marks on the tape. Fig. 5 shows an exploded view of three concentric cylinders 42, 48, 52 of a photo-electric telegraph transmitter, similar to that described in Specification 472,728, [Group XL]. As in that Specification, a radial beam of light from a source outside cylinder 52 is directed towards the axis of the cylinders and a photo-electric cell is responsive to light reaching the inside of cylinder 42. A message tape bearing a printed five-unit code moved tangentially to cylinder 52 which is rotated so that slots 56 in it, in turn, register with successive lines of the code marks on the tape as they pass through the light beam. Cylinder 48 is geared to cylinder 52 so that it rotates once for a movement of cylinder 52 corresponding to the distance between adjacent slots 56, and slots 50 scan the individual units of the message code. Cylinder 42 is stationary and slots 46 serve to transmit, to the photocell, light resulting from the message scan. The use of light conducting rods to permit convenient location of the photocell is described. Slots 54 in cylinder 52 co-operating with slot 49 in cylinder 48 and slot 44 in cylinder 42 serve to scan starting impulses. The modification according to the invention, is the provision of equally spaced control marks near one edge of the tape and corresponding slots 57 on cylinder 52 so that when correct relative phase obtains between the tape and cylinder 52 no light is transmitted through slot 47 of cylinder 42 to a second photocell 64, Fig. 6. Transmission of light to this cell under out-of-phase conditions, however, energizes through a thermionic valve amplifier-oscillator including valves 132, 139, a relay 119, to operate a clutch 107 and disconnect a friction drive 105 to a tape feed roller 66 and, if necessary, apply friction brake 114 to slow down the feed, which would be otherwise fast, until the relative phase is corrected. In Fig. 6, photocell 63 is that influenced by the message code and operates a relay 153 through a thermionic valve amplifieroscillator to transmit the message impulses over line 157 to a printer at a distant station.