No Dial tone

Check the phone line were it comes into the house there is usually a point where the phone connection from the the TELCO outside wires connects to the inside wiring.
Remove the inside wiring and test the wiring that is on the TELCO side. If you get dialtone the trouble is in the inside wire. If you don't get dialtone call TELCO

I assume you cannot get dial tone on your Vtech handsets or base unit. The phone is telling you that another phone or device has seized the line, therefore it cannot give you dialtone. You could have another phone or device(fax, modem, etc.) off hook or you could have trouble on the line caused by bad wiring, faulty line cord, or bad outlets. To find the trouble, you need to remove all devices from all outlets and try to isolate the bad wiring, line cord or outlet by connecting a standard good phone to one outlet at a time using a known good line cord. If you are unable to isolate the trouble using this method, try going to the outside interface box and testing the line there. Inside the outside interface box there is normally a test jack with a short line cord plugged into it, unplug the test jack and plug your standard phone into the test jack. If you don't get good dialtone then the trouble is with the service provider and you need to report it to your service provider. If you do get good dial tone then the trouble is in the building wiring, outlets or phone devices. Typically there is more than one pair of feed wires from the interface box to the building outlets. Remove all but one pair, then go inside and check all outlets for dialtone(plug standard phone into each outlet one at a time) to find which are connected to the pair of wires that are still connected at the interface box. If you find trouble on this feed wire( can't get dialtone at any of the outlets), remove it at the interface box and connect a different pair of feed wires, go inside and test all outlets again. If a feed wire tests good(you get dialtone on at least one outlet) then do not remove that feed wire at the interface box and just add the next one at the connection terminals in the interface box then retest your outlets again. Work your way through all of the feed wires and outlets in this manner to isolate where the trouble is. A bad wire, line cord, outlet or phone can produce a short or partial short across the telephone wire pair that will appear to your Vtech phone as if a parallel set is in use. It can sometimes take quite an effort to locate a bad wire or outlet. Good luck.

Is the fax machine on? (Are the lights or screen lit up?) Make sure that the line going from the fax machine to the wall jack is plugged into the LINE port on the fax machine, and not the TEL port.

Try plugging a regular phone into the wall jack where the fax machine is currently plugged in... do you get a dialtone? If so, the problem is either with the fax machine or the way it is configured.

I know it sounds foolish, but be sure the phone jack you're plugging in to actually has dialtone. Make sure the line cord you're using is good, and is firmly plugged in until the latch snaps in. Sometimes the plug may seem like it's in but isn't making a good contact.

If it still says there's no dialtone, try reinstalling the modem drivers. Then start looking for a replacement modem.

Remove the phone line from the back of the fax and connect a standard phone (not a business PABX or PAX system phone) to the line. Ensure dialtone is available. (Make sure in doing this that you are also testing the cable from the phone socket to the fax). If no dialtone, replace cable or fix line.

Check that the line is connected to the 'line' port on the fax, not the 'phone' port.

If still no dial tone, it may be modem fault (in the fax). Seek specialist attention.

The modem card is faulty. It needs to be replaced.

try downloading updated drivers for your modem and...please make sure the phone cord is plugged into the line side and not the side with the pic of a phone on the modem.

You need to check your modem setting under control panel, there is a "wait for dialtone" option that you need to untick. Please let me know if this fixes the problem.

Very strange that there a no other symtoms.

Are you sure you are plugged into the LINE port of the fax machine?

The error 680 means There is no dial tone. The modem is not detecting a dial tone There are many possible causes of a No Dial Tone Error. 1.Check cable is correctly inserted into back of modem and phone socket 2.Check properties of connection, make sure correct modem is being used 3.Disable "wait for dialtone before dialing" in My Computer > Dial Up Networking > Properties of Connectoid > Configure > Connection > remove checkmark under call preferences 4.Try removing fax machines or other devices connected to the line 5.Make sure no one is using the telephone when trying to connect