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In article <3685@tank.uchicago.edu>, barry@arthur.uchicago.edu writes:
> A friend recently showed me a "technique" for making free phone
> calls from a payphone... <description of grounding the microphone>

} <excellent details from Larry Lippmann>

During my highschool days it was possible to get a dial tone on a pay 
phone by peeling a spot of insulation from the handset cord and 
touching the bared wire to the phone's keyhole.  Handset cords weren't 
armored then, nor were the handset caps screwed on by King Kong.  I 
hadn't heard of the method of grounding the microphone by piercing the 
diaphragm, but even back then there were special pay-phone mikes which 
had louvered hard-metal covers so that a sharp object stuck through a 
hole in the mouthpiece grille would not damage the mike.

A kid who lived near a telephone exchange used to dive their dumpster 
regularly.  He recovered enough stuff to build his own neighborhood 
phone system.  His best find was a coin mechanism from an old-style 
pay phone.  Coins rolled down a ramp, then took different paths 
according to size and velocity.  A magnet trapped steel slugs.  
Nickels and dimes hit cup-shaped bells, quarters hit a coiled-spring 
gong similar to a Seth-Thomas clock chime.  There were two contact-
microphones on the mechanism.

Long-distance operators listened to the sounds and counted the money. 
My friend found that the coin/bell mechanism would make the desired 
sound effects when held near the mouthpiece.  (It still cost 10 cents 
to activate the phone initially.)

I once worked at a YMCA camp where the only phone was a pay unit.  We 
discovered that a large pot from the kitchen  made acceptable 
"quarter" sounds when struck.  One guy made a long-distance call and 
"paid" for it by banging on the pot; after "depositing" the required 
amount, he continued to strike the pot.  When the operator told him 
"That's enough money," he replied, "You've been such a good operator, 
I'm giving you a tip."
"No!  Stop!  They don't give it to me!!"  she said.

Depositing coins in modern pay-phones triggers electronic tones, which 
supposedly can be faked with a simple device.  "Phone Phreaking" was 
popular in the '70s but seems to have become passe.  TPC (The Phone 
Company) prominently published claims of sophisticated countermeasures.

Another kid-type phone hack which a friend from Chicago says they used 
do at O'Hare Airport:  Put raw egg-white in the coin return, then 
observe from a distance-- Along comes Mr. Spiff businessman and makes 
a credit-card call, after which his coin is returned.  He reaches for 
the coin, contacts nasty goo, goes "YUCK!!" and _leaves the money_!  
It doesn't work anymore, with electronic credit-card readers and 
phones which require no initial coin.

--

Frank Reid     W9MKV @ K9IU   reid@gold.bacs.indiana.edu
{inuxc,rutgers,uunet!uiucdcs,pur-ee}!iuvax!silver!commgrp