Patent GB-612730-A (GB)
Title: Improvements in sound and picture transmission systems
IPC: H04N7/084
Filed: 1946-03-28
Abstract: 612,730. Sound and picture transmission systems; television. SCOPHONY, Ltd., and WIKKENHAUSER, G. March 28, 1946, No. 9699. [Class 40 (iii)] A system for the transmission of pictures and sound comprises a transmitter arranged to impress sound signals and picture signals successively upon a single transmission channel, means for applying a switching signal to the channel and a receiver having a sound reproducer and a picture reproducer of the imagestorage type and switching means responsive to the switching signals for transferring the received signals from the sound reproducer to the picture reproducer. As shown in Fig. 1, the output from a microphone 2 is connected over a conducting arc 19a on a disc 11a to a transmitter 3 and aerial 4. When a picture is to be transmitted, the operation of a key 5 energizes the coil 6 of a magnet 8 lifting a latch 9 allowing discs 11a ... 11d to rotate in an anticlockwise direction. A conducting strip 19b on the disc 11b energizes a circuit 21 to produce a switching signal from the transmitter 3 and a conducting arc 19d controls the voltage supply to the grid 25 of the cathode-ray tube 22, whilst a conducting arc 19c connects a scanning generator 23 to the deflecting plates 28 so that the beam scans the plate 27 on which the picture 29 is imaged. When the discs 11a . . . 11d are arrested by the engagement of the latch 9 with a notch 32, the picturescanning mechanism has already been disconnected and the microphone 2 is again connected. At the receiver, Fig. 3, with the switching discs 42a ... 42d in the positions shown, the received signals pass to a loud-speaker 45 over a path .including a conducting arc 43a of the disc 42a. A circuit 37 selectively controlled by the switching signal operates an electromagnet 38, 39 which allows the discs 42a ... 42d to rotate. The conducting segment 43b connects the receiver 36 to the control grid of the cathoderay tube 47 whose scanning generator 48 is controlled over a conducting arc 43c on the disc 42c. When the disc assembly is arrested by the engagement of the latch 40 with the notch 55, the loud-speaker 45 is again connected to the receiver 56. To restore the transmitter to the position shown prior to the transmission -of a further picture, the key 5 is operated and during the rotation to bring the notch 10 to the stop position a segment 19b<1> on the disc 11b effects the transmission of a further switching signal from the transmitter 3. At the receiver the corresponding rotation of the disc assembly connects a circuit 56 over conducting sector 43d on the disc 42d to erase the existing picture from the screen 50, if the picture reproducer is of the type described in Specifications 513,776 and 524,230 in which relatively opaque deposits are formed on a screen of crystalline material. In a modification, the receiving cathode-ray tube may have a fluorescent screen with a long afterglow. The switching signals may be similar and differentiated from the picture signal by amplitude or duration. In the arrangement shown, the first switching signal may be a predetermined frequency in the audible range, whilst the second signal is preferably outside that range. The scanning period for the picture may be much longer than that required for normal television transmission. The arrangement may be such that in response to a single switching signal, the existing picture is erased prior to the reproduction of the succeeding-picture.