1.3.4 Telephone line connection (LINE a b)
The basic condition for NLLW operation is telephone line connection.
Telephone line is 2 wires which you connect to screw terminal up picture 3.
Picture 3: Telephone line connection
Telephone line interface has following typical parametres. The voltage in
Hang up status (disconnect loop) 20-60V = (during connection not depends on
polarity), when NLLW pick up (active status) on telephone line is cca 7-12V,
depends on line current which is in range 20-60mA. Further telephone line
parametres are signalling, ringing (incoming call) is define by AC voltage from
50-90V and frequency 20
– 60Hz. To the signalling belongs even tones, have
frequency 425Hz +/- 20Hz and level -10dBm (cca 0,22V) and difference lis
cadency. The NLLW reacts on those tones.