[VoIP] [Strowger] Re: [originally from Strowger] A NYC Payphone Puzzle

[Steph Kerman]

Hi Bernard,

In a digital office, the tone would have to be within the passband of 
the anti-aliasing filter of the subscriber line codec.  I'd guess that 
the transmitter has a wider passband than the filter, which cuts off 
quite abruptly around 3KHz.  In Automated Coin Telephone Service, toll 
deposits are detected at the TSPS tandem office.  Therefore the coin 
deposit tones would need to be detectable over a 3KHz T1 channel.

I do believe that the first coin deposit changes a DC condition in the 
telephone that can be interrogated by the COE.  So the COE can determine 
whether one or more coins or the "initial rate" is actually in the 
hopper.  AFAIK, to use a red box successfully, one should deposit one 
nickel or perhaps the inital rate first and then use the red box for the 
remaining deposits.  This way, if the COE performs an intial rate or 
coin presence check before call completion, it will succeed.

Steph

Bernard Green wrote:
> Steph
>
> I cannot recall from where I heard this but I do recall an attempt to beat the red box hacking  by using a tone that was outside the working frequency range of the microphone. 
>
> The use of an intelligent ( but not vandal proof  ) phone for pay phones would remove the need to have fee checking on allocated lines in the exchange.
>
> Regards
>
> Bernard Green
> Dead ringer for a Wanna bee telephone engineer
>
>
>
>
> ----- Original Message ----- 
>   From: Steph Kerman 
>   To: ATCA ; ATCA-Yahoo Group ; TCI ; Central Office ; VoIP ; Strowger List 
>   Sent: Monday, October 09, 2006 8:20 PM
>   Subject: [Strowger] Re: [originally from Strowger] A NYC Payphone Puzzle
>
>
>   Interesting thoughts, Bernard.
>
>   The majority of Telco owned payphones in the US are connected to "coin 
>   lines".  Privately owned payphones use ordinary lines with intelligence 
>   inside the payphone and would be vulnerable to the "hack" you described.
>
>   On coin lines, there would be no extra benefits from having metallic 
>   access to the line since the COE rates the call and supervises for coin 
>   deposits.  The transmitter is enabled from the moment dial tone is 
>   received, so arbitrary tones can be sent by acoustic coupling without 
>   metallic connection.  Indeed, the "red box" does precisely this, 
>   emulating coin deposit tones.
>   It would probably be much easier to get access to the line by opening 
>   the base of the pedestal, which I think is assembled with "security" 
>   Allen screws having a center post, requiring a hollow Allen driver.
>
>   Although 2 dial leads are visible hanging out from the front opening, 
>   I'm pretty sure even a modernized dial implementation has at least 3 
>   leads.  But probably it has 5 or more leads since traditionally, the 
>   receiver was muted first by separate contacts to prevent audible clicks, 
>   the transmitter was then disabled and the line was then switched to the 
>   oscillator last.
>
>   However it is interesting that they pulled these two leads out through 
>   the front holes.  That may indeed be a clue.  I'll have to try out that 
>   phone and see whether it is a dumb phone on a coin line or a smart phone 
>   on an ordinary line.  I am not aware of Verizon using smart phones 
>   within their own service area.
>
>   Steph
>
>   Bernard Green wrote:
>   > First thing that comes to mind is that having gained access to the wires to the touch tone keypad a more versatile tone generator could be connected. This may provide " extra benefits" to the vandal in routing calls.
>   >
>   > Maybe the two wires to the keypad would allow an ordinary phone to be connected to the line and thus bypass the coin operated switches
>   >
>   > On UK coin boxes where the microphone was shorted until coins had been inserted "vandals" would slit the sheath of the cable ( coin box to phone ) and snip the brown wire to prevent the short being applied.
>   >
>   > Bernard Green
>
>
>
>    
>   Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
>  
> Yahoo! Groups Links
>
> <*> To visit your group on the web, go to:
>     http://groups.yahoo.com/group/Strowger/
>
> <*> Your email settings:
>     Individual Email | Traditional
>
> <*> To change settings online go to:
>     http://groups.yahoo.com/group/Strowger/join
>     (Yahoo! ID required)
>
> <*> To change settings via email:
>     mailto:Strowger-digest at yahoogroups.com 
>     mailto:Strowger-fullfeatured at yahoogroups.com
>
> <*> To unsubscribe from this group, send an email to:
>     Strowger-unsubscribe at yahoogroups.com
>
> <*> Your use of Yahoo! Groups is subject to:
>     http://docs.yahoo.com/info/terms/
>  
>
>
>
>
>   

-- 
General request: Please *DO NOT* send messages with attachments larger than 300K total to this JPS email address without my prior agreement.  Send those messages to me at stfkerman at gmail.com.  I have a small mailbox at JPS. Large attachments will interfere with my email and cause other messages to bounce.  If you don't know how big the attachment is, please send it to stfkerman at gmail.com.  

Thanks.