GB1113373A - Improvements in or relating to television apparatus - Google Patents

Abstract

1,113,373. Multiplex radio signalling. RADIO CORPORATION OF AMERICA. 15 Nov., 1966 [7 Dec., 1965], No. 51822/65. Heading H4L. In a dual standard television receiver, such as one for the reception of 405-line V.H.F. signals and 625-line U.H.F. signals, separate tuners and intermediate frequency amplifiers are provided for each kind of signal, but the sound components at intermediate frequency of one kind of signal only are extracted and are amplified in the I.F. amplifier for the other kind of signal. As described, video signals at intermediate frequencies from the output of a V.H.F. 405-line tuner 10, Fig. 1, are amplified, detected, and further amplified in units 14, 22, 24, respectively. Audio signals at intermediate frequency are extracted by a tuned circuit (Fig. 2, not shown) and are taken to the input of a 625-line I.F. amplifier 16. The intermediate frequencies are so arranged that the 405-line sound carrier and its side-bands fall within the pass band of the 625-line intermediate amplifier and that the 405 video carrier and its sidebands lower in frequency than the sound carrier fall outside the pass band of the said amplifier. A unit 20 detects the output from the amplifier 16 and produces a 405-line audio frequency output. When the receiver is switched to 625- line working, the detector 20 produces 625-line sound signals at intercarrier frequency, and these are further amplified in a unit 26 and are finally detected in a unit 28. The 625-line video signals at intermediate frequencies from the output of the I.F. amplifier 16 are detected in a video detector 18 and are amplified in the unit 24, which is switched from the 405-line detector 22 when 625-line signals are being received.