Detection circuit for a video tape recorder signal
US4942472A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 6, 1988 |
| Grant date | Jul 17, 1990 |
| Priority date | — |
| Expiry date | Dec 6, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/126
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A detection circuit for a video tape recorder signal on the input of a TV set connected to a line synchronization separating circuit (11) in turn connected to a PLL (12) comprises a first phase comparator (15), the PLL (12) exhibiting a first time constant (I1, C1) corresponding to an operation on a normal TV signal. This circuit further comprises a switch (20) for switching the PLL on a second time constant (3I1, C1) shorter than the first one, a second phase comparator (22) for comparing the input and output phases of the first phase comparator, the second phase comparator being associated with a third time constant (I2, C2) shorter than the first and second ones, a threshold comparator (24) supplying to the switch (20) a control signal when the comparator output (22) is outside determined limits.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.