The Stereo FM Tuner
was yet another add-on for the Project
60 modular hi-fi system. As the name suggests,
it was a radio tuner component, covering the 87.5 to
108 MHz frequency range.
Its main selling point was what Sinclair claimed to
be a novel innovation - its use of the "phase lock
loop principle", as "used for receiving signals
from space craft because of its vastly improved signal
to noise ratio". You would not have had much luck
picking up Sputnik on the FM Tuner, but it was a reasonably
useful product that continued to sell until Sinclair
got out of the audio market in the mid-1970s.