3 or 4 rings are required before the incoming call is signalled

I'm using Trioxbox 2.8.0.3 with a TDM410 card, with 4 FXOs modules, and one of the attached lines is made out of an ATA (that is, an adapter connected to the cellular network and taking calls as if they were from the conventinal PSTN). It works almost well, except that 3 or 4 rings are required before the incoming call is actually sent to the intended extensions. Is there any parameter that can control/avoid such artificial delay? Thank you.