View Full Version : Crosstalk on unterminated HMP analog fxo lines

10-29-09, 10:00 AM

The application is a simple voice recording application based on speech detection. What is happening is the voice call is coming on one port which is recorded based on speech detection. But a speech detection event gets fired on other ports also where nothing is connected. Also these are not adjoining ports. For an actual speech detection event in port 1 a similar speech detection event gets fired in port 6. On recording of the same speech gets recorded in port 1 & 6 both.


An unterminated analog line, left on hook, has a very high impedance and therefore is susceptible to crosstalk. The solution therefore is to make sure all your lines are terminated (i.e. connected to the telco/switch) or disable any unterminated lines in software (do not call PKH_TRUNK_Start for them).