This circuit makes use of a specific 80's component and was found in an American manual of the time. A matrix keyboard allows you to select one of several music programs.
Taiyo Yudem SAW filters can be ordered from Mouser Electronics for UMST (W-DMA), GSM, CDMA, LTE,...
This “people detector” with pyroelectric sensor was found in the April 1991 issue of Radio...
This circuit is from an American magazine that no longer exists, Modern Electronics, in a February...