Good call by ProfTech. From the Callcentric help page for the Telemarketer Block
"This feature was developed to reduce/eliminate unwanted telemarketing and robocalls.
When activated, inbound callers (to the DIDs that you have this feature activated on) will hear an automated message which will require them to press a specific key (1 through 9) in order to complete their call. Your Callcentric Phone WILL NOT begin to ring, until the inbound caller has successfully pressed the requisite key on their phone.
You have the option of assigning a specific number (1-9) that you would like your caller's to press in order to complete your call or you can have the number that your inbound callers need to press randomly assigned on a per call basis by choosing the "Random Digit" option.
**Callcentric Tip: If you would like to avoid having your friends, family, and colleagues have their calls intercepted by our Telemarketer Block Feature (when calling from familiar/known numbers) we suggest adding their numbers to your Callcentric Phone Book and setting up a prioritized Call Treatment to route calls from these known numbers directly to your phone. In doing so calls from these known numbers will reach you void of any intermediary message and calls from any unknown numbers will be prompted to press the requisite key (1-9) in order to complete their call."