Patent GB-1423421-A (GB)
Title: System for controlling electronically the operation of tv  receivers
IPC: H04N5/00
Filed: 1973-02-09
Abstract: 1423421 Control of TV receivers; gain control; digital-to-analogue conversion ITT INDUSTRIES Inc 9 Feb 1973 [10 Feb 1972] 6525/73 Headings H3Q H3T and H3H In a control system for controlling the programme selection and/or operating functions such as sound volume, timbre, brightness, contrast, colour saturation, chromaticity of a black and white or colour television receiver in which the variation required in the channel frequency or operating function is effected by a control voltage applied to a controlling element, on the actuation of a corresponding control contact la (Fig. 2) a binary coded value corresponding to the programme or operating function is used to access the corresponding row of a main store 8 and cause the value of the frequency or operating function stored to be pulsed out to set a forward-backward counter 3 accordingly. A clock pulse frequency 11 is applied to the forward/backward counter 3 via a frequency divider 10 and the changed status of the forward/backward counter 3 is transferred periodically to a D/A counter 4 for modifying the response of the controlling element and transferred also into the selected storage row of the main store 8 to modify its contents until the required programme frequency or operating function value has been set by the controlling element and the corresponding control contact has been released and restored to normal. As shown in Fig. 2 the receiver is controlled by operating contacts on a control panel la such as push buttons or touch contacts to select a tuning frequency. The associated code from a code converter 6 is fed into an auxiliary store 5 in which the number of the chosen programme selector contact is stored. The stored information is then fed via a multiplex circuit 7a, 7b which select one row of the main store 8 corresponding to the frequency selected and the information relating to the frequency band. The setting of the forward/backward counter 3 is effected by the binary value of the receiving frequency selected and counting in the backward direction from this particular value provides at the output of the counter 3 a number of pulses corresponding to the binary value. The clock pulse frequency of the counter 3 is obtained from 11 and a frequency divider 10 and may be the colour or chrominance subcarrier frequency divided by eight of a colour TV receiver or in a black and white TV receiver may be an internally produced auxiliary frequency corresponding to the colour subcarrier frequency also divided by eight. The required control voltage occurs at the output of the D/A converter 4. Further information concerning the selected frequency band is fed to the tuner via a decoder 9. The stored frequency for a contact can be adjusted by readjusting the forward/backward counter 3 depending on the sign of the modification selected at the control panel 1a by counting pulses in either direction until the operating contact has been restored to normal. A further circuit (Fig. 3, not shown) may be provided which is similar to Fig. 2 and has further multiplex circuits (14a, 14b) associated with the D/A converter 4 for controlling the sound volume, timbre, brightness, contrast, colour saturation and chromaticity. The associated control panel part (1b) has the operating contacts required for setting the above control quantities permitting variation in opposite directions. The digital to analogue conversion of the binary value of the control quantity may be obtained by the circuit shown in Fig. 4 where the frequency divider 10 of Figs. 2 and 3 comprises a chain counter 10a and flip-flops 10b and 10c. When the forward/backward counter 3 is counting to zero FET T3 is conducting and capacitor C1 is charged via R. Charging ends when the counter 3 reaches zero and T3 turns off. At the end of the maximum possible charging time FET T2 conducts so that charge on C1 is transferred to C2 which provides the control voltage. When T2 turns off FET T1 conducts to discharge C1. The circuit of Fig. 4 performs an integration of the counting pulse from the counter 3. Digital MOS integrated circuits may be used. Storage of the control setting when the receiver is switched off is obtained by maintaining a supply voltage to the setting or adjusting electronics such as by an accumulator arranged to be charged when the TV receiver is turned on. Ultrasonic remote control of the TV receiver is possible.