Pen recorders and phone records

I have read that if the police want to know who a person communicates
with on the telephone, they can arrange to have a "pen recorder" put on
their phone line.  This will record all phone numbers called from that line.
Supposedly the legal barriers to this type of surveillance are much less
than for a phone tap.

I am confused about the necessity for this if the phone companies routinely
record this information anyway.  Is this just an archaic and obsolete
terminology, and what really happens is that the phone company will give
already-existing phone records to authorized officials?

Thanks -
Hal

The Secret Service also refer to devices that record incoming phone 
numbers as pen registers.

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> I am confused about the necessity for this if the phone companies routinely
> record this information anyway.  Is this just an archaic and obsolete
> terminology, and what really happens is that the phone company will give
> already-existing phone records to authorized officials?

Hal,  I'm not sure, but a pen register would record all dialing codes
(touch tone), not just those used to make the first leg of the call.
Voicemail, multihop calls, etc come to mind.

Eric Blossom

On Thu, 17 Feb 1994, Eric Blossom wrote:
> Hal,  I'm not sure, but a pen register would record all dialing codes
> (touch tone), not just those used to make the first leg of the call.
> Voicemail, multihop calls, etc come to mind.

I believe that they do.  I dialed tons of extraneous #'s when I thought I 
was being DNRed.  I also discussed various bogus murders with some of my 
friends.. it was quite interesting.  You can never be too safe.. 
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