to the input 46 the output 47 is connected to an output terminal 49 of the television circuit the output terminal 49 carries picture information ps 39 which is derived in a manner that will be described in more detail from the supplied picture information ps the switching input 48 of the switch over device 45 is connected to the output 3 of the source 1 the switch over device 45 is drawn as a mechanical switch with two switching contacts t1 and t2 which are connected to the respective inputs 46 and 44 contact t1 and t2 are connected to the output 47 during the field periods tv1 and tv2 respectively in practice the switch over devices 32 37 and 45 will have the form of electronic switches the input 33 of the switch over device 32 is connected to the junction point 7 39 between the output 7 of delay device 6 and the input 8 of delay device 9 so that the input 33 carries the instantaneous line information b1 the input 38 of the switch over device 37 is connected to the junction point 13 39 between the output 13 of delay device 12 and the input 14 of delay device 15 so that the input 38 carries the instantaneous information a1 the use of the halving circuits 29 and 26 ensures an equivalent signal supply namely a1 relative to.