Frequency out/DTMF out Filter
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Has any one perfected a output filter other than just a resistor and
capacitor on the output of the stamp to get relatively pure sine waves
out? And more importantly, when outputting a DTMF signal, a filter
that produces equal amplitude outputs of the high and low frequency group?
By just using a resistor (10K) and a filter capacitor (0.01 uF) causes the
high order
group to be down in amplitude by approximately 50%. This causes undesirable
"twist" error which the DTMF reguards as a false signal.
capacitor on the output of the stamp to get relatively pure sine waves
out? And more importantly, when outputting a DTMF signal, a filter
that produces equal amplitude outputs of the high and low frequency group?
By just using a resistor (10K) and a filter capacitor (0.01 uF) causes the
high order
group to be down in amplitude by approximately 50%. This causes undesirable
"twist" error which the DTMF reguards as a false signal.