Synchronizing device for a television scanning equipment

Claim 1

A synchronizing device allowing it to give to the signals from a television scanning equipment a variable phase lead relatively to an input synchronizing signal from a central control, said equipment comprising a camera unit, a channel control unit and cable means for linking said camera unit and said control unit at an adjustable distance from each other, said synchronizing device comprising camera circuits located in said camerA unit and channel control circuits located in said channel control unit, and said input synchronizing signal being the mixed line and field sync. signal, or enabling such a signal to be reconstituted,the received or reconstituted mixed line and field signal being referred to as the ''''input mixed sync. signal'''' ; said camera circuits comprising : a line frequency generator having a phase control input ; said control channel circuits comprising : means for receiving said input synchronization signal : a phase comparator having a first input for receiving the line sync. pulses of the input mixed sync. signal, a second input, and an output coupled to said phase control input ; a controllable variable delay device having an input coupled to said line frequency generator and an output coupled to said second input of said phase comparator ; a generator producing signals at a frequency equal to 4 qF , q being a positive integer, followed by a divider circuit which enables three signals of frequencies F 1/T , 2F and 4F to be obtained, and a phase control loop locking the phase of said last mentioned generator to that of the line sync. pulses of the input mixed sync. signal ; and a phase-lead field frequency circuit for generating a field blanking signal having a lead, relatively to the phase of the corresponding signal associated with said input mixed sync. signal, said phase-lead field frequency circuit comprising a further adjustable variable delay device, and a counter coupled thereto ; a coincidence circuit for receiving said signals of frequency 2F and 4F , and the input mixed sync. signal, the output signal from this circuit, for each field period, being formed by n (n being a positive integer) pulses of duration T/8 each of which coincides in time with part of a field sync. pulse of the input mixed sync. signal, said n pulses of duration T/8 being applied through said further adjustable variable delay device to reset said counter to zero, said counter having two outputs and comprising two decoders for respectively supplying two pulses at said two outputs of the counter when the latter passes through two given states, said phase-lead field frequency circuit further comprising a bistable multivibrator , having two inputs respectively connected to said outputs of said counter , for delivering said field blanking signal with a phase-lead.