I R C U I T D E S C R I P T I O N; H A N D S E T - Philips SPENDEX 40 Maintenance Manual

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S P E N D E X 4 0 U A 8 2 5 1 / 0 0 A N D / O l L I M I T E D M A I N T E N A N C E M A N U A L
4 C I R C U I T D E S C R I P T I O N
This chapter gives a functional description of the various circuits.
The circuits are described per module on the basis of the block
diagrams of Fig. 4-1, Fig. 4-2 and Fig. 4-3.
4 . 1 H a n d s e t
4 . 1 . 1 M i c r o p h o n e
The microphone converts the speech signal into an electric signal.
The signal thus obtained is directed to the microphone amplifier on
the connecting board.
4 . 1 . 2 T e l e p h o n e
The telephone makes the signal, which comes from the telephone
amplifier on the connecting board, audible.
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4 . 1 . 3 P t t - s w i t c h
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The Ptt-switch should be used during a secure conversation in the
Half Duplex transmission mode (equipment type UA 8251/00). Every time
the Ptt-switch is pressed, the Ptt-signal is activated.
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