SYNC. MESSAGE: periodic, ‘synchronized’, message. Either sinusoidal, or sinusoidallike
(‘sinuous’), its frequency being a sub-multiple of the MASTER CLOCK (being any
one of four frequencies selected by an on-board switch SW2). A message synchronized
to the system clock is convenient for obtaining stable oscilloscope displays. Having a
recognisable shape (but being more complex than a simple sine wave) gives a qualitative
idea of distortion during the decoding process (examined in a later experiment). See
Table A-1 in the Appendix to this experiment for more details.