You can tell your phone is tapped when you hear a snicker in the background when you are being all mushy with your significant other.
First Method
1.
Call 202-543-9994
2.
Listen for a steady monotone signal with no interrupts. That means you are not being tapped. If you hear any interruptions in the signal tone, then you are being listened to.
Second Method:
1.
Call 101028817709889664
2. They will first repeat the phone number you are calling from and then repeat a bunch of zeros. The number at the end of the zero’s is what is important. If it is a 1 - you have never been tapped and are not presently tapped.
If it is a 2 it means you have been tapped in the past but no longer are tapped.
If it is a 3 it means you ARE being tapped presently and you need to be careful what you say over the phone.
Source
And they use digital equipment, not analogue, so the tappee won't know they
are being tapped.