Ramsey Electronics LABC1 Manual de Instruções descarregar pdf (Página 7)

DCI1 • 7

line. Protection diodes D10 and D11 limit the incoming signal on the phone

line (between +12.7 and - 0.7 V) so that potentially damaging voltages like the

90 Vp-p ‘Ring’ signal does not blow up Q6!

So far we have covered most of the circuitry on the board with exception of

the power supply. VR1 and the surrounding parts C3, C4 and the polarity

protection diode D1 form a simple voltage regulator to supply a steady 5 VDC

to the ICs on the board. By using this scheme, we can operate the unit with a

single 12 VDC (positive tip on J5) source and have access to the multiple

voltages needed for the unit to operate.

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Ramsey Electronics LABC1 Manual de Instruções Página 7