System 4 main functions:

1. One door station can support four hundred indoor phones at most.
2. Network application optional.
3. When in network system,the door station can have a dual communication with the management unit.
4. Remote unlocking and three kinds of chord melody rings optional.
5. With card reader function,you can unlock the door by card.
6. There are two kinds of indoor phones available which can be connected to the door station.Please see the pictures for those indoor phones shown on the right(Character: Indoor phone).