All DSL can experience drop-outs caused by the Telco equipment. If you have checked the modem at another known "good" installation and it works faultlessly, then it's almost certainly your DSL service. Telstra in Australia will tell you that it's acceptable for drop outs of approximately two a day. Mostly these will "mend" themselves within the router dead timer, which is in the router configuration. You may not be able to see it, depending on what flavour you have. If it works elsewhere then insist that your Telco/ISP checks with their Network Engineers on your service. If the network guys insist everything is OK, you have to believe them as their tools will find the problem if one exists. Then you have to look elsewhere, change cables, filters, look at whether the alarm system, if you have one is playing up. Talking of filters, if you have anything bigger than one voice handset and the modem, then you may need to look at central filtering. To do this spend a couple of hundred and get a cabling expert in to resolve it, especially if you have alarms or other equipment.
Keyhole Kate, February 2012