While we don't have an ATLAS with more than 27 DSP resources, that only prevents more than 27 SIMULTANEOUS calls.
I'm also afraid there is no way to add DSP resources to the ATLAS.
The DPS resources are used to "generate dial tone, generate Ring back, generate digits to be propagated out of the unit." So as long as the calls aren't initiated at the same time, you can have more than 27 calls active at the same time. The ATLAS 830 actually supports 10 PRI to RBS conversions (but the DSP resource limits it to providing dial tone to only 27 channels at a time).
The dial tone is independent of the PRIs. So the USER TERM RBS T1's should provide dial tone regardless of the state of the PRIs. (This is because calls can be routed to other USER TERM entries, or possibly out various NETWORK TERM entries - so the RBS T1 will stay "up" and provide dial tone no matter what the condition of the other interfaces.)
I suggest either monitoring to see if specific channels are failing to provide dial tone, or even going through each T1 channel to verify every channel receives dial tone. You can monitor the T1 in the ATLAS to verify it sees the channel go off hook as well.
Hope this helps a little,
Thanks for the information. Yes, we have validated that it isn't any particular channel(s). A channel will get no dialtone and then immediately work the next time it tries to dial (say, 30-60 seconds later). They also do come off hook and go back on hook consistently from the Atlas's perspective with no issues.
It's just a simultaneous call issue problem. Out of 144 channels (6 user RBS), we just experience conditions where more than 27 come off hook at the same time. Anyway, I do appreciate the information as that does close a loop as far as whether or not there's a different Atlas we should be using.