Sometimes, when a user hangs up, the TBB line rings back and when you answer, there is no one there. This is simply not a TBB or VoIP issue. The ringback problem has existed for years, even with regular phone systems.

You need to ensure that the hook switch is depressed for at least one second when you hangup or between subsequent phone calls - use the "Rls" or "End" buttons instead of the hook switch. Note that sometimes you may inadvertently (or through bad habit) rattle the hook switch when hanging up - either by banging or dropping the phone handset into the cradle.

In all cases, whenever the phone system does not "detect" that the hook switch has been depressed for one second, it believes that you are pressing the "flash" or "link" button. The phone system thinks that you want to make a second call - and places the first call "on-hold". Whether you actually hung up or dialed another number and then hung up, the first call is still "on-hold"! When you finally hang up, the system waits for a few seconds and then calls you back to remind you about this!

These are perfectly normal responses and not errors! So be careful how you hangup your phones!

Following are some other reasons that cause a ringback:

1. A cheap phone - Some phones do not always provide the correct electrical signal when you hang up. A simple solution is to try using a different phone. Note that it is always best to try using one phone connected to the ATA at a time. Phones that are still plugged into the ATA (via house wiring or splitters) may still have an affect even when you are not using them in this test.
   
2. Wire or jacks - Verify that the phone cords, wires, and jacks on the wall or ATA are not loose or frayed.
   

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In some instances, if you had called someone with a voicemail system, you will hear their voicemail prompts, or you might have hung up just after their voicemail prompt ended. In either case, you may be saying "hello...hello..." which gets recorded on the voicemail system! When the other person listens to their voicemail, they usually cannot understand or find it quite funny that someone has left a "hello" message!