This sounds like a modem problem. It probably has to do with resistance in the customer's loop. If the total resistance in the loop is too high, dial tone will not be provided from the telco. Resistance in the telco loop may be varying slightly at...
UPSR is better in situations where you don't care how many time slots are available on your ring. If you have more than 5 or 6 drop nodes on the ring BLSR may provide you with more circuits on the ring. As long as everything is provisioned correctl...