Philips SPENDEX 40 Maintenance Manual page 29

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NATO CONFIDENTIAL
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 . 1 3 L i n e i n t e r f a c e b o a r d
4 . 1 3 . 1 L i n e o u t p u t a m p l i fi e r
This amplifier amplifies the signal to be transmitted. The signal to
be transmitted can be the output signal of the microphone amplifier,
the output signal of the dialling tone generator or the output signal
of the modem.
4 . 1 3 . 2 L i n e i n p u t a m p l i fi e r
The line input amplifier amplifies the received signal.
4 . 1 3 . 3 I n t e r n a l / e x t e r n a l m o d e m s e l e c t o r
Under control of the comsec controller the internal/external modem
selector brings the internal or external modem into the connection.
4 . 1 3 . 4 M o d e m i n t e r f a c e
The modem interface takes care of the coupling between the equipment
and an external modem in accordance with CCITT-recommendation V28.
4 . 1 3 . 5 R i n g i n g s i g n a l d e t e c t o r
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The ringing signal detector converts a received ringing signal into a
signal of 500 Hz. This 500 Hz signal (WEK) is directed to the
telephone amplifier on the connecting board. As soon as the handset
is picked up (signal HOOKSWN active) the ringing signal is blocked.
4 . 1 3 . 6 C l e a r / s e c u r e r e l a y
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The clear/secure relay RE4 is energised, as soon as the comsec
controller activates the IM108 signal.
4 . 1 3 . 7 E x t e r n a l - l o o p r e l a y
For test purposes the comsec controller can, by means of the signal
M0D141, energise the external-loop relay RE5, as a result of which
the (internal) modem output is connected through with the (internal)
modem input.
4 . 1 3 . 8 2 - w i r e / 4 - w i r e s w i t c h i n g r e l a y
When the 2-wire/4-wire switching relay RE6 is energised the equipment
is in 2-wire connection, if not, in 4-wire connection. The comsec
9 9 2 2 1 5 4 1 3 4 3 1 4 - 1 5
NATO CONFIDENTIAL