Now monitor the audio input at tpl4 and the output from the Foster-Seeley block at tp53, using t to trigger the oscilloscope. The output at tp53 should contain two main components: li) A positive DC offset(ii) A sine wave at the same frequency as the audio frequency sinewave at tpl4 but shifted in phase by 90 the previous detectors investigated, there was also a significant amount of high frequency ripple present but this is very much less in the case with the Ratio