Patent GB-375422-A (GB)
Title: Improvements in or relating to television systems
IPC: H04N7/14
Filed: 1931-03-27
Abstract: 375,422. Television. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Ives, H. E. ; 32,.Laurel Place, Montclair, New Jersey, U.S.A.) March 27, 1931, No. 9425. Convention date, April 8, 1930. [Class 40 (iii).] Relates to a two-way television and telephone system and consists in providing a predetermined position for the user, preferably in the form of a chair at a fixed distance from the scanning apparatus. An indicator shows when the chair is occupied so that the operator may make any initial adjustments. The user is located within a booth 80, Fig. 3, the door of which actuates a switch 141 so that the photoelectric cells are out of circuit when the door is open. The user 7, Fig. 1, on occupying the chair 27 closes contacts 46 and on rotating the chair to face the scanning apparatus closes contacts 47 completing the circuit of a signal lamp 52. A bar 30 mounted in front of the chair further limits the position of the user. The booth is lit with amber light and is ventilated through vents 107, 108. The user is scanned by blue light from a source 1, passing through a shutter, lenses 2, a tube 3, scanning disc 5, a variable angle prism 31, and a blue filter 4. The output of the photo-electric cells mounted in sections 87, 88, Fig. 3 (represented by a single cell 8, Fig. 1), is tapped at 12 to illuminate a monitoring lamp 14, co-operating with the disc 5 and viewed by the operator through a lens 15 and a prism 16. The operator adjusts the angle of the prism 31 so that users of different stature may be scanned. The variable angle prism comprises two prisms 145, 146, Fig. 6, mounted in a rotatable support 147 provided with bevel gearing 149 rotated by a knob 118. The received signals energize a small glow lamp 24 co-operating with a scanning disc 25 and a lens 150 magnifies the glow lamp to fill the view, a lens 32 being adjustable vertically so that the user may view the received image in comfort. Light from the source 24 is also reflected by a mirror 33 cooperating with the disc 25 to provide in the mirror 35 a monitoring image for the operator. A microphone 61 and a loud-speaker 62 are provided out of sight behind screens and out of range of the scanning apparatus and with their axes in parallel planes to prevent interference. The loud-speaker is placed so that the sound appears to come from the received image. Alternatively, the loud-speaker may be replaced by an ear-piece. The motors 6, 26 are included with the motors at the other station in a synchronizing circuit 40 and power is supplied from a 10-volt D.C. source through terminals 43. An oscillator OSC adapted to generate oscillations of a fixed frequency is used to control synchronism. It may be connected into circuit by a switch 44. The motor 26 may have the frequency of its supply changed at 45 to adjust its speed to that of the transmitting motor at the other station. The discs are preferably rotated 18 times per second and have 72 apertures. Preliminary framing adjustments are made by scanning at each station a mirror reflecting only blue light which is obscured when the chair 27 is occupied. When the lamp 52 is lit at one station, a similar lamp 59 at the other station is energized over the order-wire lines 55 or 56 so that the operator is advised that the user is in his correct position. The local operator raises the shutter from the source 1 and observes the image through the monitoring attachment 14, 15, 16, and adjusts the prism 31 until the image is framed. The adjustment of the lens 32 may also be made by the local operator in accordance with the adjustment of the prism. A shutter 36 prevents the user seeing the image of the other user while adjustments are being made. The local operator may adjust the receiving apparatus to obtain a correctly framed image as seen through the monitoring attachment 33, 34, 35. The operators advise each other over lines 55, 56 when the adjustments have been made. On lowering the shutter 36, so that the user may see the received image, the relay 38 is opened and the armature 74 opens the shortcircuit across the winding 65 and enables the users to converse over the lines 64, 66. A speech monitoring device enables the operator to supervise the conversation and consists of a resistance 69 of 250 ohms, resistances 70 of 3000 ohms each, resistances 71 of 850 ohms each, and a jack 68. Specifications 292,546, 297,152, [both in Class 40 (iii), Telegraphs, Electric], 354,853, 374,974, 375,407, and 376,309 are referred to.