Block calls on a landline: a glossary of carrier features and plug-in devices

Most of the confusion about stopping calls on a home phone is vocabulary. A provider offers "selective call rejection," the box in the drugstore says "call blocker," the handset menu says "block list," and all three sound like one thing while doing different jobs in different places. This glossary sorts them out. Read it once from the top, then keep it as a lookup for the next time a plan page or a manual throws a term at you.

One idea runs through every entry. A call can be blocked in three places: at the carrier, at a device on the wall, or in the handset. A carrier block covers every phone on the line, including the old beige one in the hallway. A device or a handset only protects what is attached to it. Most homes end up using two of the three, and which two is a matter of what your provider sells and what you already own.

Where the blocking happens

Carrier-level blocking

Blocking done inside your phone company's network, before the call reaches your wall jack. Every phone in the house benefits, corded or cordless. It is usually the cheapest place to start, but what exists depends on your exact plan, so your bill or the provider's help page is the authority and not this page.

Personal block list

A list of numbers you add yourself, also sold as "selective call rejection." On many landlines you dial a star code right after the unwanted call (*60 is common) and follow a recording, or you edit the list in your online account. It holds a fixed number of entries, and since spam callers rotate through numbers, the list never finishes.

Plug-in call blocker

A small box that sits between the phone and the wall jack. It reads the caller ID information as a call arrives and decides whether to let it through, using rules stored in the box. Some keep a block list plus an approved list. Others ask unknown callers to press a button or say their name before the phone rings. Check that it works with your line type, copper or a VoIP adapter, and how many numbers the list holds.

Handset block list

The version built into many cordless sets: a button adds the most recent caller to a list kept in the base station, and later calls from that number are ignored or cut off. It protects the phone system the base controls and nothing else, so a corded phone plugged straight into the wall rings as usual. When the list fills, a new entry may replace an old one or be refused, which is why a number you blocked months ago can start ringing again. The cordless block button guide has the wording that goes with it.

Features on the provider's menu

Star code

A short code starting with * that you dial from the handset to switch a feature on or off. *60 for a block list, *77 for anonymous call rejection and *87 to turn it off are the patterns I see most, but there is no universal standard, and a code that works for one provider can do something else on another. Dial it once, listen to the recording and write down what it said.

Fast busy signal

The rapid beeping you hear when you dial a star code your plan does not include. It is a common result and not a mistake on your side. The next place to look is the provider's online account, since several of them keep block lists there.

Anonymous call rejection

A carrier feature that turns away callers who hide their number; they hear a recording and your phone never rings. It also stops honest callers who withhold their number, such as some doctors' offices. Read the full piece on anonymous call rejection before you decide.

Spam or robocall filter

A carrier setting, usually in the online account, that labels or diverts calls the provider considers likely spam. It is a guess about the call, so a real one can be caught. Labels such as "Spam Risk" or "Scam Likely" are estimates, not verdicts.

Call screening and do not disturb

Features that send unknown callers to voicemail or ask them to say their name first. They vary widely between providers, and on some plans they exist only on VoIP lines.

Approved-callers mode

The reverse of a block list: the phone rings only for numbers saved in its phonebook, and everyone else goes to voicemail or silence. It suits a house that gets few calls from outside the family. The cost is that a doctor's office or a school, calling from a number you never saved, goes unanswered until you check the messages.

What shows up on the screen and the line

Caller ID

The number, and a name if your plan includes one, sent by the carrier between the first and second ring. A box or a built-in display decodes it. No device can show what the carrier did not send, which is the main point of the caller ID box comparison.

CNAM

Caller name: the database lookup that supplies the name next to a number. The field is short, often about 15 characters, which explains chopped names. Why the names look strange goes through it.

Hidden number

A caller who asked for the number to be withheld, perhaps by dialing *67 first, which hides it for that one call and does not work on toll-free numbers or 911. Your screen shows "Private," "Anonymous," "Blocked" or nothing.

Unknown or out of area

Usually means the number did not arrive at all, for technical reasons, for example when a call crosses between different kinds of networks. It looks like a hidden number but is not the same thing.

Spoofing

Faking the number a call shows, often with one that looks local. It is why blocking by number is a weak tool against automated dialers, and why a familiar-looking prefix proves nothing. The number reader can tell you the region of a code, never whether the call is honest.

STIR/SHAKEN

A call-signing standard that carriers must use under the TRACED Act of 2019. It helps show that the starting network handled the number honestly. It does not make the call honest: a signed call from a rented number can still be a scam.

Terms that sit next to blocking

Do Not Call Registry

The Federal Trade Commission's list, running since 2003, which covers sales calls from lawful telemarketers and leaves out political calls, charities, surveys and scammers. People often confuse it with blocking; why it still rings untangles the two.

Robocall

A recorded or automated call. If one gets through, do not press a number to be removed and do not answer questions. Hang up.

Reporting

Scam attempts go to ReportFraud.ftc.gov, and complaints about unwanted calls to the FCC consumer pages. Neither agency will answer about your single call, but the reports help them spot patterns.

Porting

Moving your number to another provider. A block list kept in the old carrier's network usually does not come along, while a list in your own handset or plug-in box stays with the hardware. The move guide has the details.

One thing that is not a term but belongs here: some households keep the landline on a strict filter and use a separate mobile number for web forms and shop checkouts. It is a human fix rather than a technical one, and it works because the number that ends up on marketing lists is not the one your mother calls.