Rotary Phone / Measuring phone line voltage

i've pulled out old arduino! ready try again

i've got rotary phone connected voip ata. ata expects dtmf tones, old phone can pulse-dial. i've seen several arduino projects people connect inputs rotary dial. want connect arduino inbetween ata , phone.

output of cisco ata ~42-48vdc when phone idle. 6-8vdc when phone in use, , 50+vac when phone ringing. using bridge rectifier can turn of these voltage dc.

next, i'm using voltage divider bring down safe arduino. measured on multimeter, i'm getting ~1.1v when in use, , ~3v when idle.

when connect 5v psu ata directly analogue input + ground, 1023. perfect! when connect divided voltage on phone line output, crazy scatter of valued jumping , down. used code gets mode of 100 values , seems - why inaccurate?

i've never been able results when measuring voltages generated external. couldn't smooth input resister or capacitor seems i'm not going able fast accurate reading ata? (when rotary dial pulse dials, approx 10 pulses per second, isn't - when there's lot of noise amongst it, makes readings difficult).

there commercial devices 'dial gizmo' (and power line) www.dialgizmo.com


any advice? there must way.

so turns out bridge rectifier responsible noise. need new way of dealing higher ac voltages... might try single diode.

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