Consumers Put Robocall-Blocking Devices To The Test

While we wait for phone companies to get around to offering services that help consumers block unwanted prerecorded robocalls, there are already several options available for people to use now, but not all of them may be up to the task.

For their latest issue, our colleagues at Consumer Reports asked volunteers to try out four different devices — and one online service — that are intended to minimize the number of annoying calls users receive.

Most of the options use at least one approach known as “whitelisting,” where the device allows calls from phone numbers it has been told are acceptable by the user. Some of them simultaneously use the blacklist approach that uses a database of known spam phone numbers to automatically block or redirect calls. Only one of the tested options uses blacklist-only for vetting calls.

Now to the testing results.

Consumer Reports asked each volunteer to install the call blocker they received. Over the course of four days, the volunteers monitored the number of robocalls that got through. Volunteers also provided feedback on ease of setup and use.

Digitone Call Blocker Plus

Selling on Amazon for around $100 plus shipping, this device uses block black- and whitelist tech.

While some of the testers were confused with the setup instructions, three-out-of-four said they would buy it after having given it a test run.

Among the more appreciated features was the fact that it blocked calls silently. Incoming robocalls would be indicated visually, but no ringing phone or other audio alert.


Nomorobo works by intercepting all calls right after the first ring and immediately comparing the incoming number to its vast blacklist of known robocallers and the user’s whitelist of known safe numbers. If it deems the call safe, it continues to ring.

This free service, which won the Federal Trade Commission’s first public contest to create a robocall blocker, got great scores from testers — 85% of them gave it at least 4 out of 5 points — it does have one notable drawback for consumers still on traditional landlines: Nomorobo currently only works on VoIP phone service. Landline Call Blocker


Some testers were turned off by the fact that this device requires the user to actively blacklist numbers with the press of a button. And some said that even after telling the device to block a number, calls continued to come through.

That said, about half of the testers said they would purchase this product, which currently sells for around $58 on Amazon, while the others would not.

CPR Call Blocker Protect
CallBlocker Protect

At around $50 on Amazon, this is the least-expensive device in the CR test, but it also fared the worst with testers.

The product uses a whitelist-only approach, meaning that all incoming calls will be blocked until the user enters acceptable numbers.

“This was a huge setback, as there is no possible way for me to program every caller I need to answer,” wrote one tester. And this person wasn’t alone; 80% of testers said they would not purchase the device (see UPDATE below for more information related to this device).

UPDATE: Consumer Reports now notes that the CPR Call Blocker is marketed primarily for vulnerable consumers — including those with Alzheimer’s — who wish to only receive calls from specific numbers. For these users, the device should serve its purpose.

CR volunteers also tested the Sentry Dual Mode Call Blocker and the feedback was decidedly mixed. Callers have to prove they are not robots by listening to a recorded message and pressing “0” to be connected to the user. Some testers says this confused callers into thinking they had dialed a wrong number, especially since the prerecorded message is in a British accent.

Since the volunteers did their testing on the Sentry, it’s been replaced by the Sentry 2.

For more on Consumer Reports’ look at the robocall problem, check out this story from the current issue.

And to add your voice to the chorus of consumers calling on phone companies to give us easier access to call-blocking technology, you can join in Consumers Union’s End Robocalls campaign.

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