[conspire] robo calls

[Nick Moffitt]

Rick Moen:
> Doesn't work on all telco carriers:  The carrier must support a
> feature called Simultaneous Ringing.

In the early 1990s my family was targeted by some harassing phone calls,
and we started to screen everything via our answering machine.  We'd
inform people we trusted that we were doing this, so they'd tend to
leave messages while we were out that consisted of "Hello?  Hello?  Hi
it's me.  Are you home?  Okay well anyway I just wanted to chat was
all..."

I realised that a lot of the telemarketer recordings and pushy
salespeople were getting onto the tape.  And I'd read in some punky
Usenet source or phreaking G-file that the trick for getting rid of
these people for good was to put the SIT sequence at the start of your
outgoing message:

    https://en.wikipedia.org/wiki/Intercept_tone#Other_uses

That Wikipedia page lists the exact frequencies and tolerances, but the
text I read listed the notes to play (I seem to remember it started with
B-flat above high C, and then the others were in the octave above that).
The theory was that call centres valued the salespeople's time enough
that they didn't connect them if their war-dialled number turned out to
be disconnected.

Allegedly you could play the three tones in a quick triplet, and the
enemy system wouldn't be picky enough to tell the difference from a
genuine intercept message.  I pulled out my cheap synth and tried it.
My impression was that the pushy salespeople became rarer and the
recorded messages more frequent. 

But that could have just been the shifting winds of telemarketing.
My synth may not have been true enough to the frequencies used by
telecomms stuff, or I may not have even played the right notes!