I have a system running 1.4 r81383 built from source using a TDM400P for external POTS lines. My Polycom SIP phones are on the same network (no NAT).
Sometimes, but not everytime, when making an outbound external call, the called party picks up and the caller can hear them, but there is a 3-10 second delay before the called party can hear the caller.
I’ve played around with echo cancelling/call progress settings, but nothing seems to have an effect.
The destination of a call appears like it has an effect, but my sample size isn’t big enough for me to make that claim. It seems to not happen when I call other landlines, but it does happen when I call cell phones or lines through FIOS service.