GB1240361A - Synchronising arrangements for television systems - Google Patents

Abstract

1,240,361. Automatic phase control. PYE Ltd. 23 April, 1969, No. 20745/69. Heading H3A. In a synchronizing system, a synchronizing signal from a remote point is compared with a local one, and is delayed in response to the phase difference detected to produce a residual phase error which is less than a given value, the residual phase error then being removed by a further phase control arrangement. In a first embodiment; Fig. 1, a signal from a remote station is applied at A, and is fed through two. delay networks 1 ... 9 and 10 ... 17 to a phase detector 20 where it is compared with a signal from a local generator 21 to produce an error signal which is fed to control unit 24. If the error is greater than a first reference level, switch S1 is actuated via motor M1 to insert delay until the error signal falls below the first reference level. When this occurs switch S2 is actuated via motor M2 until the error signal falls below a second reference level. The resulting residual phase error is then eliminated by a control loop in the slaving unit 25 which locks the two signals. This control loop may be of the type in which pulses are added to or subtracted from the input to a divider. In an alternative arrangement, Fig. 2 (not shown), binary delays are digitally controlled by a phase comparator of the type which counts the number of pulses from a clock source (40) which occur between local and remote synchronizing pulses (LOCAL, REM).