drewes@cory.Berkeley.EDU (Rich Drewes) (04/12/90)
hi hi hi, I have a few telephone electronics questions maybe you can help me with. I want to sit on the phone line and look for DTMF (dual tone multi-frequency) signals. My current circuit works by using a low impedance (8 ohm) audio 8:1000 transformer in series with the tip line. The ring line remains untouched. My circuit looks at the high impedance side of the transformer to read the signal. Question 1: Is my transformer component choice a good one? Question 2: Is there is solid state component that would perform the tapping and isolation function that the transformer now performs? Question 3: What precautions should I take on my circuit side regarding the high voltage ringing signal passing through the transformer? Are diode shunts enough protection? Thanks for your help. Rich drewes@cory.berkeley.edu