Ihave these components:
- 40 rooms
- guard house
- speaker system
- high alert indicator
- mild alert indicator - in use indicator

i was given these function of the components:
a) the intercom must have a connection from the gate to each room and from each room to another room. to reduce cable runs and minimise cost, a single cat5 cable runs from the room to a central switch in the building. another cable runs from the switch to the gate. this is shown in figure 1 below.
b) connection is establish by entering the room number into the keypad following by some call button. the room number is translated into a unique binary address embedded in the system.
c) when a room is called the buzzer is sounded and a visual indicator blinks on panel in the room.
d) if the call is accepted and the line is busy, all other terminals will have the in use indicator lit.
e) each alert indicator must have a unique code. these function is only activated by the college manager to all connected device. when alert is high, the buzzer must also ring for 30 seconds.

i am confused about drawing a flow chart giving the input conditions and discuss the process for room 5 on the intercom with the gate.

, any idea or close to my question is very much appreciated.