Matt Blaze
And speaking of telephone mischief, here’s a Dianatek model 041 pen register, designed for use not by law enforcement, but by telephone companies. The telco security department would hook this up to your line (at the central office) if you were suspected of making harassing calls or otherwise misbehaving with your service. It also detects signals used by blue boxes, despite being made well after they were obsolete. Resembles a movie prop bomb that starts a short countdown when you open it.
May 3, 2023 at 10:39pmWeb
Show threadMatt BlazeMay 3, 2023
Cc @SteveBellovin
Show threadMatt BlazeMay 3, 2023
The main difference between this and the pen registers used by law enforcement was the usage model. This is a suitcase designed to be left at the central office, producing a daily printout on paper tape. The pen registers used by police provide a real-time link back to the investigators’ wiretap plant, where they are immediately alerted any time the target uses their phone.
Show threadMatt BlazeMay 4, 2023
Physical pen registers for analog phone lines are mostly (but not entirely) an obsolete technology at this point. Aside from the diminishing importance of analog telephony, wiretapping and dialed number recording features have mostly moved into the phone switches themselves (helped along by mandates in the Communications Assistance for Law Enforcement Act).
Show threadFritz AdalisMay 3, 2023
@mattblaze
I don't see a pen
Show threadOrinMay 3, 2023
@mattblaze Can that function between a telephone and a VOIP ATA gateway?
Show threadMatt BlazeMay 3, 2023
@auroran yup
Show threadSteve BellovinMay 3, 2023
@mattblaze And here's a 1920s pen register, seen at the Museum of Communications in Seattle.
Show threadThatcher UlrichMay 4, 2023
@SteveBellovin oh that's great!
Show threadScott ThompsonMay 3, 2023
@mattblaze I bet this thing was used to try and catch the likes of Kevin Mitnick and others doing telco social engineering
Show threadClaraMay 3, 2023
@mattblaze there's a small part of me that wonders what use cases that power outlet would have in day to day operations, what kind of additional equipment might be used in connection with this, et cetera.
Show threadMatt BlazeMay 4, 2023
@rallias It has interfaces for audio recording (contact closure and audio out); perhaps the jack is intended to power that.
Show threadChris StroupeMay 3, 2023
@mattblaze We definitely need more electronic devices built into briefcases.
Show threadtippenringMay 4, 2023
@mattblaze I'm a little surprised that it has the ABCD keys. I guess autovon use perhaps?
Show threadMatt BlazeMay 4, 2023
@tippenring No, it doesn't seem to generate dtmf at all. The keypad is just to enter phone numbers, set the time and date, control the printer, etc.
Show threadMatt BlazeMay 4, 2023
@tippenring It does *decode* the full 4x4 DTMF keys (as well as MF), however.
Show threadtippenringMay 4, 2023
@mattblaze fascinating. During design they were probably thinking 'we already have thousands of these pushbutton keypads in the warehouse, may as well use them for this.'
Show threadMatt BlazeMay 4, 2023
@tippenring There have always been a few niche applications outside autovon for A-D, including some signaling in automatic call distributors, idle signals in wiretap systems (C tone), and a few others here and there.
Show threadtippenringMay 4, 2023
@mattblaze back in the late 90s when I got into telecom, my employer sold a voicemail product from a company called AVT. We could use ABCD for a type of inband signaling. IIRC I think it used those tones to exchange messages between systems in cases where a large org had several of them. It was really pretty ingenious.