In Australia there was a Blue Coin Phone that used the telco line
(effectively a normal POTS line with metering pulses) to supply all
the power to operate the coin mechanism.  Solenoids etc.

After it was installed for the first time it would take a little
while, about 5 mins to charge up the capacitor before the phone could
be tested.

It had all the components that a pay phone would need.  Ie
Microprocessor, display, coin mech etc.

Cheers Justin

On Mon, May 12, 2008 at 9:28 PM, alan smith <micro_eng2@yahoo.com> wrote:
> Thanks for all the information.  I'd prefer to leave the power in a battery, and if it will run for 6 months or a year on a couple of AA batteries, then that should actually be a little easier to design around.
>
> Robert Ammerman <rammerman@verizon.net> wrote:  >>Bob Ammerman:
>>> I am guessing that he milli-amp level current allowed at 200V is still
>>> below
>>> the real trip current for an off-hook condition.
>
>
>>From: "David VanHorn"
>> You have to draw at least 20mA to guarantee being detected as off-hook.
>
> I should have said below the 'maximum guaranteed stay-on-hook current.'
>
> -- Bob Ammerman
> RAm Systems
>
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