Disconnection of the communication line when handset is on hook

Switching on and off of the current supply when the handset is off hook or on hook

Audio and visual signaling when there is an incoming call

Control and signaling for short circuit or disconnected line when sending an outgoing call in LB mode

Visual signaling for discharged current source

Operation over two-wire line with attenuation up to 44 db for frequency of 800 Hz

Frequency range from 0,3 to 3,4 kHz

Call signalling with frequency of 252 Hz and no load voltage from 80 Veff to 100 Veff not less than 70 Veff at 10 k load and not less than 50 Veff at 3 k load

Protection against over voltage and atmospheric discharge