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The Charging Box (c) Stinky Pig Productions
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What it does:
The Charging Box is used to indicate when a call is being charged
for and when it is not. Once installed, the box has two lights, a
green and a red. Green means free and red shows that you are being
stung by BT!
Components:
1 x green LED 1 x circuit board
1 x red LED 2 x 10K ohm (1/4 watt) resistors
2 x short lengths of wire 2 x small bulldog clips
Circuit Diagram:
| Line |
| (50v) |
|------ ------|
| |
|-----[]------O------|
| |
|-----[]------O------|
Where [] is a resistor and O is an LED.
NB. IMPORTANT! One LED should have it's anode towards the resistor
and the other should have it's cathode towards the
resistor.
Connection:
Build that onto the board and connect the two points marked line
to the wire, with the bulldog clips at the end. The box should now
be connected to the line in parallel with the phone.
Operation:
When the line is opened (Ie. the phone lifted) the green LED will
light (if the read one does then just reverse the polarity of the
box). Dialling numbers (by pulse) will cause the green LED to flicker
but while you are making free calls it should never go out and the
red LED will not light. As soon as the exchange starts charging for
your call, the green LED will go out and the red LED glow.
How it works:
As the LEDs are in opposite directions, only one can light depending
on the polarity of the current supply. This is exploited when
the exchange begins charging as the polarity of the line is
reversed.
Downloaded From P-80 Systems 304-744-2253