Does anyone have any information on the Racal MA290 Signal Comparator Nato nummber 5820-99-951-0656. We have one at the Radio Communication Museum of GB but have no information whatsoever. It looks as though it compares the incoming signal with the internal 5MHz and 1MHz sources and prints the difference on a front panel printer. I would guess it is late 1960s or early 1970s manufacture. It uses transistors throughout but no printed circuit boards. Steve G8EBM