Philips SPENDEX 40 Maintenance Manual page 17

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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 . 3 C o n n e c t i n g b o a r d
4 . 3 . 1 M i c r o p h o n e a m p l i fi e r
This amplifier amplifies the analogue signal which comes from the
microphone.
4 . 3 . 2 L o w p a s s fi l t e r t r a n s m i t t i n g s i d e
The low pass filter transmitting side is the first circuit on the
transmitting side of the vocoder. The filter limits the frequency
band of the amplified microphone signal to approx. 3600 Hz.
4 . 3 . 3 A / D - c o n v e r t e r
The A/D-converter samples the signal limited in band width with a
frequency of 8 kHz and converts each sample into an a-law code of 8
b i t s .
4 . 3 . 4 D / A - c o n v e r t e r
The D/A-converter converts the digital signal, which comes from
synthesis processor 2 on the synthesis board, again into an analogue
s i g n a l .
4 . 3 . 5 L o w p a s s fi l t e r r e c e i v i n g s i d e
The low pass filter receiving side is the last circuit on the
receiving side of the vocoder. The filter limits the frequency band
of the analogue signal to approx. 3600 Hz.
4 . 3 . 6 Te l e p h o n e a m p l i fi e r
This amplifier amplifies the signal destined for the telephone. This
signal can be the output signal of the vocoder limited in band width,
the output signal of the line input amplifier, the ringing signal,
the output signal of the dialling tone generator or the pre-emption
s i g n a l .
4 . 3 . 7 C I K - i n t e r f a c e
The CIK-interface takes care of the coupling between the equipment
and the CIK-module. When the CIK-module is removed at a moment that
the apparatus is in a state, in which the CIK-module should be
connected, the interface will produce a CIK-alarm (CIKAL).
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