How does a telephone call take place? Stallings and Slyke, 1997
1. Picking up a receiver is signaled to the end office switch
2. The switch responds with an audible dial tone to indicate that a number can be dialed
3. the caller dials the number (communicated to the switch as a called address)
4. if the called subscriber is not busy, the switch alerts that subscriber to an incoming call by sending a ringing signal which causes the telephone to ring
Feedback is provided to the caller by the switch:
- if the called subscriber is not busy, the switch returns an audible ringing tone to the caller while the ringing signal is being sent to the called subscriber
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- If the called subscriber is busy, the switch sends an audible busy signal to the caller
- If the call cannot be completed through the switch, the switch sends an audible reorder message to the caller.
6. The called party accepts the call by picking up the receiver which is signaled to the switch automatically
7. The switch terminates the ringing signal and the audible ringing tone and establishes a connection between the two subscribers
8. The connection is released when either subscriber hangs up