GB1145563A - Visual display system employing a cathode ray tube - Google Patents

Abstract

1,145,563. Television. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. 18 March, 1966 [20 March, 1965], No. 11991/66. Heading H4F. In a television transmission system switch means are provided in a receiver which in one switching position direct received television signals (picture and synchronization signals) to a picture reproducing tube, and in the other position direct received pulse coded information for symbol, i.e. linear, representation, e.g. alpha-numeric characters, via decoding circuits to the picture reproducing tube, the transmitter being arranged to transmit television signals and coded information signals which may be preceded by switching-over signals, e.g. pulse code control signals, for switching over the receiver switch means. As shown, Fig. 2, a high-frequency voltage S is demodulated DB to produce voltage U which controls a video output station VE and a pulse discriminator ID which responds to switching-over signals (A), Figs. 1b and 1c (not shown), causing switching of contacts i, u, v and h of switch UW. Discriminator ID may be an amplitude or time discriminator or a counting circuit. For normal television reception the switch contacts i, u, v and h are as shown and the picture signals pass through contact u to the cathode of tube AR. The synchronization signals are filtered out by amplitude filter and separation stage AI and control a vertical deflection device VA and a generator and discriminator GD for the phase synchronization with horizontal deflecting device HH in which the high voltage for the screen AR is also produced. If switching-over signals are transmitted, e.g. five pulses instead of a frame synchronization signal, Fig. 1b (not shown), discriminator ID responds thereto and switches over contacts i, u, v and h so that contacts v and hare open, contact u is in position 2 and contact i is closed. The transmitter then transmits pulse coded information for symbol representation which is passed from output stage VE to pulse former IF where it is regenerated and passed to control unit LW which separates the signal into co-ordinate control components (symbol positioning on the screen of tube AR) and symbol selection components. The positioning information is stored in register ZD and converted through digital-analogue converters DA 1 and DA 2 into corresponding voltages for the main deflection coils HA. The symbol codes are supplied to symbol generator ZG and the resulting beam control signals are passed via digital-analogue converter DA 3 to an additional deflection coil ZA or to the main deflection coil HA to cause the electron beam to record the particular symbol composed of portions of straight lines which may be combined with preshaped symbols. Switching- over signals may be derived from synchronization pulses in the receiver or the transmitted switching-over signals may be used simultaneously for the synchronization of the receiver, and manual switches and/or automatic switching means may be provided in the receiver. Thus the television signals and coded information may be transmitted in regular alternation so that not only may one or other of the pictures be selected but the symbol information may be faded into the television picture. For this arrangement the synchronization pulses may be at least partially replaced by the coded information, part of the coded information being transmitted during the interval between two frames and continued in the next interval.