hi,
is it possibile to use 4046 as a tone decoder ?
I'd like to use the hook indicator as detector for a 440Hz sine wave
signal...
The XOR phase detector will work with a fair amount of noise. You need to
prevent huge spikes from getting to the PLL chip so there is likely to be
a resistor in the input signal path. You will also need a capacitor in
series to allow the PLL input to self bias.
Vcc
!
--- 1N914
^
! 2.2nF !
--/\/\---+--+-------+-----!!----! Sig in
22K ! ! !
--- ---
1N914 ^ --- 22nF
! !
GND GND
You will want a counter chip so that the VCO output can be made to run at
4 times the 440Hz input. Assuming there is enough noise, you can decode
the "I'm locked" signal with a quad XOR gate chip.