On Tue, 14 Jul 1998 15:56:53 -0400 Sean Breheny <shb7@CORNELL.EDU>
writes:
>On Fri, 10 Jul 1998, Peter L. Peres wrote:

>
>Please excuse my ignorance, but what is the bulb for? Just to get an
>indication that the phone is drawing current?

The bulb replaces a resistor to limit the current.  Using a bulb is
better because it is not linear.  Over a rather wide range (from when it
starts to glow up to full rated voltage), a bulb will approximate a
constant current source.  In the olden days, special "ballast bulbs" were
made for this purpose.  I think they used a different metal for the
filament, maybe iron.


>
>Thanks,
>
>Sean
>

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