I have 6 x 3660 routers on offshore platforms connected to Mitel PABX's with either E&M or FXO, satellite connection to office onshore 3660 routers with e1 card with PRI Qsig connected to Meridian 61c and DASS connection to PSTN from Meridian. All appears to work OK except for when dialling a PSTN number which is busy, user is receivng ring tone instead of busy tone, (works OK to a busy office extension). Has anybody suffered from this or be able to advise. 3660 using 12.2 (19b).