Method and apparatus for transferring commands from the control site to the recording site in closed loop television installations

Claim 2

In a method for the transfer of commands from a control site to a recording site in a closed loop TV installation of the type provided with a recording site which includes TV camera means actuated for generating a video signal including linesynchronizing pulses, a frame-synchronizing pulses and postequalization pulses, and a control site including monitoring means and controlling means operable for delivering commands to the TV camera means, and wherein a cable interconnects the recording site and the control site so as to transfer the video signal from the recording site to the control site, the improvement comprising, for each command from the control site, lowering of the level of a predetermined number of the linesynchronizing pulses included in the video signal, said lowering being actuated by said controlling means at the control site and extending along the entire cable, and, at the recording site, detecting the lowered-level line-synchronizing pulses, and converting the counted number of lowered-level line-synchronizing pulses into a signal whose magnitude and destination are determined by and are a function of said counted number.

Claim 3

A method according to claim 1, characterized in that it comprises, at the control site, bringing the lowered-level line-synchronizing pulses back to the original level before they reach the monitoring means.

Claim 4

A method according to claim 2, characterized in that it comprises maintaining the start of each level lowering in a preselected time relationship with the frame-synchronizing pulses preceding said start.

Claim 5

A method according to claim 3, characterized in that it comprises selecting said time relationship so that the start of the first level lowering which follows each group of frame-synchronizing pulses is delayed after the post-equalization pulses.

Claim 6

A method according to claim 4, characterized in that it comprises selecting said time relationship so that the start of each level lowering falls within an interval between two consecutive line-synchronizing pulses.

Claim 7

A method according to claim 5, characterized in that it comprises comparing the number of the lowered-level line-synchronizing pulses and a predetermined variable number and producing the end of the level lowering wheN said numbers are equal.

Claim 8

A method according to claim 6, characterized in that it comprises checking the coincidence between the lowered-level pulses and the line-synchronizing pulses comprised in the video signal emerging from the TV camera means before counting the lowered-level pulses at the recording site.

Claim 11

An apparatus according to claim 8, characterized in that it comprises level-restoring means inserted between said level-lowering means and the monitoring means for bringing the lowered-level line-synchronizing pulses to the original level, and an unmatching stage inserted between said level-lowering means and said level-restoring means.

Claim 12

An apparatus according to claim 9 characterized in that it comprises; downstream of said level-restoring means and in parallel with respect to the monitoring means; a first synchronism separator; a first amplifying integrator connected to deliver elongate pulses each of which is started with the first, and is terminated by the last frame synchronizing pulse comprised in each half-frame interval of the signal at the output of each first synchronism separator; at least a first monostable multivibrator which is driven by each of said elongate pulses away of its stable state, a multivibrator having at least one stable state which is driven by the return of said first monostable multivibrator to its stable state away of said first stable state and is driven by said first synchronism separator so that the first synchronizing pulse delivered after said drive away causes the return thereof to the first stable state; a second monostable multivibrator which is driven by the return of said multivibrator having at least one stable state to said first stable state momentarily away of its stable state; a first bistable multivibrator for controlling said level lowering means and said level restoring means which are driven, every time that said second monostable multivibrator returns to its stable state, to be switched between a first stable state, to which correspond the deactuation of said level lowering means and said level restoring means and the closure of a gate inserted between said first synchronism separator and a first digital counter, and a second stable state to which corresponds the simultaneous actuation of said level lowering means and the opening of said gate; and at least a first decoding circuit which compares the number counted by said first counter with a predetermined number corresponding to a variable presetting thereof and drives the momentary shift of said second monostable multivibrator from its stable state when said numbers are equal.

Claim 13

An apparatus according to claim 10, characterized in that it comprises a first pulse generator which is driven at every shifting cycle of said multivibrator having at least onE stable state, to generate a resetting pulse for said first counter.

Claim 14

An apparatus according to claim 11, characterized in that said multivibrator having at least one stable state is a bistable multivibrator.

Claim 15

An apparatus according to claim 11, characterized in that said multivibrator having at least one stable state is a monostable multivibrator whose constant of oscillation is at least equal to the period of repetition of the line synchronizing pulses.

Claim 16

An apparatus according to claim 13, characterized in that there is arranged, in parallel with said monostable multivibrator, at least another monostable multivibrator having a greater constant of oscillation and that, in parallel with said first decoding circuit there is arranged at least another decoding circuit which is enabled to replace the first decoding circuit as said other monostable multivibrator returns to its stable state.

Claim 17

An apparatus according to claim 14, characterized in that said first monostable multivibrator has a constant of oscillation which is such as to delay the return of the multivibrator to its stable state beyond the group of the post-equalization pulses.

Claim 18

An apparatus according to claim 15, characterized in that said second monostable multivibrator has a constant of oscillation equal to a fraction of the period of repetition of the line synchronizing pulses.

Claim 19

An apparatus according to claim 16, characterized in that it comprises, in association with the recording site, a level detector, a second digital counter and at least a second decoding circuit having a plurality of outputs which are energized alternatingly as a function of the number of the line synchronizing pulses as detected by the level detector and counted by said counter.

Claim 20

An apparatus according to claim 17, characterized in that there is inserted between said level detector and said second counter, a coincidence detector which is connected for delivering a pulse whenever a coincidence occurs between a pulse detected by the level detector and one of the line synchronizing pulses sent thereto by a second synchronism separator connected in parallel at the TV-camera output.

Claim 21

An apparatus according to claim 18, characterized in that it comprises a second pulse generator which is driven by a second amplifying integrator fed by said second synchronism separator, to deliver a resetting pulse for said second counter at every group of frame-synchronizing pulses which is comprised by the video signal.

Claim 22

An apparatus according to claim 19, characterized in that said second decoding circuit is supplemented by at least another decoding circuit which can be substituted for said second decoding circuit.

Claim 23

An apparatus according to claim 20, characterized in that said second decoding circuit and the decoding circuit added thereto are actuated alternatingly under the control of a third and a fourth monostable multivibrator whose respective constants of oscillation are slightly lower than those of said first monostable multivibrator and said other monostable multivibrator added thereto, said third and said fourth multivibrators being driven to shift away of their respective stable states by said second amplifying integrator and driving in turn, via respective delay lines, the actuation of said second pulse generator.