In message , James
writes
There is an application that uses FSK. But the actual information is
not coded by the frequency shift but rather by the length of time one
of the pulses is turned on. The pulses are about 2 milliseconds long.
The information is coded on one of them. The other is always the
same length. The frequency shift is always a constant.

Now, my question. If you send this signal into a standard FM Rx it
will produce a tone.

Why? The two frequencies do not exist at the same time in the receiver.

Mike