Assuming an RJ11 connector, what would the correct polarity be for this
voltage (48V)?

What would be a safe way to drop the voltaje when off-hook? A series
resistor maybe?

Calvin

>To get you started,   The open circuit voltage is 48 volts (called on
hook), and the off-hook
>voltage is about 6 to 15 volts, depending on the telephone used.  A typical
600 Ohm phone should
>yield about 12 volts when off hook.  The ring voltage is about 90 volts AC,
the frequency can
>vary depending on the system (The different frequencies used to be used to
select different
>phones on a party line).  The caller ID information is sent between the
first and second rings as
>an fsk modulated modem signal at 1200 baud, as i recall.   The dial tone is
made up of two very
>accurate sine waves mixed together, so its sounds the same everywhere and
is easy to detect
>electronically.

>

>You are not supposed to hook un-registered devices to the phone line (FCC
regulates this).  Most
>phone interface circuits isolate the line with a 600 to 600 ohm
transformer, go off hook with a
>relay contact, and optically isolate the ring detection, so that no DC
connection exists between
>the line and the customer equipment.  Be careful not to accidentally
connect the phone line to a
>power supply or AC.  This could be vry very expensive for you.

>

> Regards,

>   Ron Fial

>===================================================================

>At 07:45 PM 7/9/98 -0600, you wrote:
>>Sorry to bother you again with another OT.
>>
>>Does anybody know a link where I can find info on the US telephone system
>>specifications?
>>
>>Actually, what I need to know is the voltajes that must be present on the
>>lines, and the signal levels.
>>
>>Calvin
>>
>