GB842101A - Improvements in or relating to systems of subscription television - Google Patents

Improvements in or relating to systems of subscription television

Info

Publication number
GB842101A
GB842101A GB3436356A GB3436356A GB842101A GB 842101 A GB842101 A GB 842101A GB 3436356 A GB3436356 A GB 3436356A GB 3436356 A GB3436356 A GB 3436356A GB 842101 A GB842101 A GB 842101A
Authority
GB
United Kingdom
Prior art keywords
signal
oscillations
sound signal
vision
receiver
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB3436356A
Inventor
Thomas Marmaduke Constab Lance
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rank Cintel Ltd
Original Assignee
Rank Cintel Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rank Cintel Ltd filed Critical Rank Cintel Ltd
Priority to GB3436356A priority Critical patent/GB842101A/en
Publication of GB842101A publication Critical patent/GB842101A/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/16—Analogue secrecy systems; Analogue subscription systems
    • H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Television Systems (AREA)

Abstract

842,101. Secret transmission. RANK CINTEL Ltd. Nov. 8, 1957 [Nov. 9, 1956], No. 34363/56. Drawings to Specification. Class 40 (4). [Also in Group XL (b)] In a television system, the vision signal is transmitted normally whilst the accompanying sound signal is rendered secret by a scrambling process, the nature of which is capable of alteration, and a control signal to permit privileged receivers to recover the sound signal is added to the signals in the vision channel. Preferably the mode of scrambling is changed at comparatively frequent intervals in an unpredictable manner. In one way of carrying out the invention, the sound signal is divided into three bands, each of which is arranged to be heterodyned by one of four oscillations which are selected by a control signal derived from the line-frequency synchronizing pulses. A corresponding set of four oscillations is provided at the receiver and to permit a reverse heterodyning process to be carried out the control signal is added to the vision signal preferably as modulation of a sub-carrier within the frequency range of the vision signal. The frequencies of the oscillations are advantageously chosen to be related to the line frequency or one of the carrier frequencies so that at the receiver they may be derived from the received signal and the need for receiver local oscillators avoided. In another way of carrying out the invention, the sound signal is divided into two bands, the upper band being transmitted unchanged whilst the lower band is modulated by one or the other of two oscillations for irregularly varying periods to yield beat frequency components having frequencies higher than those of the upper band.
GB3436356A 1956-11-09 1956-11-09 Improvements in or relating to systems of subscription television Expired GB842101A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB3436356A GB842101A (en) 1956-11-09 1956-11-09 Improvements in or relating to systems of subscription television

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3436356A GB842101A (en) 1956-11-09 1956-11-09 Improvements in or relating to systems of subscription television

Publications (1)

Publication Number Publication Date
GB842101A true GB842101A (en) 1960-07-20

Family

ID=10364701

Family Applications (1)

Application Number Title Priority Date Filing Date
GB3436356A Expired GB842101A (en) 1956-11-09 1956-11-09 Improvements in or relating to systems of subscription television

Country Status (1)

Country Link
GB (1) GB842101A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0322059A1 (en) * 1987-12-23 1989-06-28 Philips Electronique Grand Public Sound scrambling/descrambling system and method
GB2369022A (en) * 2000-07-08 2002-05-15 Radioscape Ltd Delivery of digital media files, e.g. by digital radio

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0322059A1 (en) * 1987-12-23 1989-06-28 Philips Electronique Grand Public Sound scrambling/descrambling system and method
FR2625391A1 (en) * 1987-12-23 1989-06-30 Radiotechnique Ind & Comm METHOD AND SYSTEM FOR INTERFERING / UNLOCKING SOUND
US4965826A (en) * 1987-12-23 1990-10-23 U.S. Philips Corporation Method of and system for scrambling/descrambling sound
GB2369022A (en) * 2000-07-08 2002-05-15 Radioscape Ltd Delivery of digital media files, e.g. by digital radio
GB2369022B (en) * 2000-07-08 2003-06-04 Radioscape Ltd Digital transactions for the delivery of media files

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