Abstract: Trigger signals both at horizontal and vertical line frequency required for an oscilloscope are derived from the horizontal synchronization output stage of a television receiver without any direct electrical connection to the receiver. A pick-up coil or tuned pick-up circuit is positioned in the vicinity of the receiver. The signals induced in the coil or circuit are applied to a comparator. The output of the comparator is at the required TTL level to provide the horizontal trigger to the oscilloscope. If a vertical trigger is also required, the comparator output is applied to a frequency doubler circuit. The output of the frequency doubler circuit is divided by 525, the so-divided output constituting vertical trigger circuits for the oscilloscope. A monitoring circuit for horizontal sync signals is connected to the comparator output and indicates the presence of horizontal sync signals by activation of a light emitting diode.