I went through what a Synchronous detector is and understand the following:
From diag. 3, Its evident that the weird transistors act as analog switches, able to conduct +/- halves of sine waves with negligible zero crossing error which then add up to give different signals based on phase diff.
The use is to ultimately extract signal proportional to phase difference between two low amplitude signals(less than noise amplitude a times) and subsequently amplify it to a DC value with an LP filter.
The inputs are input 1&2 which will be low amplitude AC. the switch is operated by voltages <24 V(possibly <20V) (diag. 2) from the other two transistors.
This link gave me those surmises:
http://measure.feld.cvut.cz/system/files/files/cs/vyuka/predmety/A3M38MSZ/SynchrDetectBW.pdf
Please advise on whether my understanding is right and suggest alternative transistors that might do the same job.
4066 might be a good choice but i am worried about the maximum Gate voltage that can be applied.