Sometimes, when I have had a load of junk cold calls on my mobile - you know the ones - had an accident recently? / claim back your PPI? / - it would be nice if it had call guardian like the landline does (but not enough to make me change phones )
Since getting a phone with Call Guardian, the cold calls went to zero, nil, zilch, none - you get the idea 🙂
An incoming call has a series of potential hurdles to surmount before the caller actually talks to me.
The first barrier is Anonymous Call Reject - like the name suggests, it is designed to reject any calls where the caller is witholding their number, they get a polite message telling them they must disclose their number to be connected.
However ACR has a few weaknesses - because it is designed to only reject calls that actively refuse to disclose callers number it is no protection to number stripping and number spoofing.
The easiest way to understand how ACR works is to imagine it as a butler receiving callers at the door and asking them for their calling card - no card, no entry; have a card, and entry is granted.
Number stripping is where the number is removed, and a blank field presented instead - it does not actively refuse to divulge the number, simply presents no number - it is a bit like giving the butler a blank piece of card, since the butler does not examine the card the butler accepts it and permits entry.
Number stripping can happen unintentionally, in certain telephone networks, where there is no direct dial number for the originating call, and as the number exits the internal network the internal extension number is dropped but no new replacement number for the switchboard substituted.
Number spoofing as the name suggests is where the originating number is exchanged for a different one - a bit like giving the butler someone elses card.
It can be done for perfectly legitimate reasons, for example to ensure any return calls are passed through a centralised call handling system eg our GP surgery, all the GPs have direct lines in their consulting rooms, but they would not want patients phoning directly at random, so the surgery switchboard number is displayed instead.
So, the call passed ACR it now arrives at my phone. It now faces the next test: Call Guardian.
Call Guardian is like an automated PA, screening all incoming calls. It runs through a few steps.
First step is: Is it a known number? ie is it on the whitelist or blacklist?
If it is a known number, and on the whitelist, then the call is put through with no further interaction from the phone.
If it is a known number, and on the blacklist, then the call is rejected and the caller informed that their call has been refused.
If it is not a known number, the next step is to identify the caller.
The caller is played a brief message asking them to identify themselves. The phone then informs me that I have an "announced call" and plays the callers message.
I now have 3 choices:
accept call - pick up the phone and talk to the caller
reject call - play the caller a message telling them their call has not been accepted
send to voicemail - direct caller to leave a message.
With the mixture of these, most cold callers and automated diallers are kept away, as they want to talk to a person not an automated response system.
Incidentally, you do not need worry about an old friend who hates machines getting locked out, the phone still records the incoming call numbers, so you can see who called, even if the phone did not ring, and ring them back / add their number to allow list