The NEC code also works with bursts of a defined
carrier frequency which is 38 kHz. All Vishay
Telefunken receiver photo modules operate well with
this system.
The NEC code starts the transmission using a
so–called leader code, a burst of a length of 9 ms,
followed by the data word after a pause of 4.5 ms. The
initial idea of this leader code is to settle the internal
control loops in the receiver modules. But for the
Vishay Telefunken receiver such a preburst is not
necessary.
As long as a key is pressed, only the leader code is
repeatedly transmitted, followed by a single bit. A
specialty of this code is the property of constant word
length in connection with a pulse–distance
modulation. Both address and command bit are