Patent GB-1521898-A (GB)
Title: Broadcast receiver channel selection system
IPC: H03J7/28
Filed: 1975-09-16
Abstract: 1521898 Radio tuning with programmable digital memory TEXAS INSTRUMENTS Inc 16 Sept 1975 [25 Sept 1974 (3)] 38004/75 Heading H3Q In a receiver tuning system having a switch 90 and/or 106, 108, Fig. 7, for obtaining a selective address or sequential addresses from a parallel output bus of an address generator 92 and/or 110 for reading from a storage location, of a programmable tuning memory 102, associated with that address a digital tuning word and a digital band selection word, the digital tuning word is converted at 103 and 118 to an analogue tuning level signal which together with the digital band selection word via 122, 124 adjust the receiver 120 to the required channel and the digital words stored at an address location can be changed by operation of 114, 116. The address generators 92 and 93 and tuning memory 102 of Fig. 7 are disclosed in detail (Figs. 12, 9 and 13, not shown). The tuning output from a D/A converter 103 is fed via an integrator 118 to a varactor diode tuner 120. Reprogramming the tuning memory 102 at an address selected by push buttons 90 or up/down switches 106, 108 is obtained by pressing both up and down programming switches 114, 116 to clear the associated storage location. By pressing the switch 114 the tuning voltage is increased. If either switch 32 or 34 is pressed longer than say 8 sec. the system switches to a fast tuning mode. When the required picture is viewed on the TV screen the switch 32 is released. Fine tuning can then be made by momentary operation of switch 32 or 34. When a UHF band is selected instead of a VHF band a signal to a select circuit (318. Fig. 13, not shown) of the tuning memory 102 is such as to select a slower clock signal to a tuning programme generator (320) so that slower tuning is achieved. A battery connected at (300) retains the stored states of the LVH, HVHF and UHF band switch and skip RAM (292) and tuning voltage RAM (294) of the tuning memory for six months from set-up. The AFC is disabled during tuning by an output 110, Fig. 7 from a gate (212, Fig. 9, not shown) at the output of the sequential address generator 93 which includes an AFC sequence counter 202 functioning to hold a selected channel (Figs. 10 and 11, not shown). Skipping desired channels is obtained by pressing the programme switches 114, 116 (322,324, Fig. 13, not shown) simultaneously at the addresses of these channels so that two "0's" are entered into the skip RAM (292). When operating in the sequential access mode a skip signal is generated from (334) to skip the unrequired channels. The D/A conversion at the output of the tuning memory 102 is obtained from a comparator (304. Fig. 13, not shown) which receives inputs from a 12 bit synchronous binary counter (306) and from the word generated from the RAM (294) through an up/down counter (302). The integrated output of the comparator (304) provides the analogue tuning voltage. Channel display can be by neon lamps 134, Fig. 7 controlled by a driver 104 disclosed in detail (Fig. 18, not shown) or in a further embodiment (Fig. 8, not shown) by a 7-segment LED display (147) controlled by a display memory (145) and a 7- segment decoder (142) which are disclosed in detail (Fig. 19, not shown). By pressing (83,711) the UHF channel number associated with a selected address can alter the UHF channel number stored in the display memory (145). Arrangements of the channel lamps and 7-segment display are disclosed (Figs. 1-6, not shown) in which indicia for switches (20) can be fixed or removable and for the lamps (38) can be removable. A microphone (18, Fig. 1, not shown) enables ultrasonic remote control of the tuning by a controller (24) which can be of the parallel or sequential access type. In the further embodiment (Fig. 8, not shown) an address generator (141) includes a latch circuit (380, 382, Fig. 14, not shown) for determining series or parallel mode of operation and a tuning memory (143) and D/A converter (144) are disclosed in detail (Figs. 15, 16a and 16b, not shown). Integrated circuits can be used in the tuning system which can be employed for television, radio and cable television tuning. Specifications 1,521,899 and 1,521,900 are referred to.