In UK back in the 90s, there were various prefix numbers you could dial before you dialled the desired number, which saved you money, one of which was "Mercury" which used 132 code. Anyway, way back in the 90s I recall we were sent a tiny box about the size of a UK phone socket, which had a BT phone plug at one end and a socket at the other - you inserted this device inline, between your phone and the phone socket, and it would detect what number you were dialling, wait until you'd finished dialling digits, then it would prepend the call saving service code in front of the number you'd dialled, then dial the whole number for you, savings code included, without you needing to do anything.
I remember taking it apart as a teenager, but I didn't make any notes as to what make or model etc, it was, nor the provider (this was wayyyyyy before my digital realm began online, so I have no records or emails).
Does anyone in the UK remember these dongle dangling thingies, where they came from or any other info? They fascinated me.
Thank you
