The signal at pin 4 is a 136.36-kHz square wave. An input within the lock range of
181.8 kHz will result in the output at pin 7 varying around its de voltage level set with input
signal at f0• Figure 13.26c shows the output at pin 7 as a function of the input signal frequency.
The de voltage at pin 7 is linearly related to the input signal frequency within the frequency
rangefL = 181.8 kHz around the center frequency 136.36 kHz. The output
voltage is the demodulated signal that varies with frequency within the operating range specified.