Huawei OptiX OSN 2500 Quick Installation Manual page 53

Installing Orderwire Phones
1
Assembling the Orderwire Phone Base
2
Installing the Orderwire Phone
Set the ring switch to "ON" and the dial switch to "T".
When installing an orderwire phone, tilt it upwards to avoid falloff.
PHONE interface
50
SEI board
Orderwire phone cable