Technical information

Issue 7 June 2001 9-1
9
Call Routing
Call Routing Call Flow
The following is the basic call flow through the DEFINITY ECS, DEFINITY G1 and
G3, or System 75:
 Endpoint signals switch to start call.
 If originating endpoint is a station, the request for service is an off-hook.
 If originating endpoint is a trunk, the request for service is seizure signal
(wink start, off-hook, ground start).
 The switch signals endpoint to start dialing.
 If the endpoint is a station, dial tone is played for the caller.
 If the endpoint is a trunk, a start dial signal (wink dial tone, etc.) is sent to
the originating end.
 The digit string is dialed.
 The first digit dialed is compared to dial plan record.
 The type of call is identified depending on the dialed digit.
 The calls can be to an extension number, trunk access code, attendant, or
feature access code.
 The number of digits needed is known after the first digit is dialed.
Example: User dials 0. Call is routed to an attendant because zero is defined as
an attendant call requiring one digit.
Example: User dials 2. Digit two is defined as a 4-digit extension code on the dial
plan form. Three more digits are required to place the call. The three additional
digits are dialed. The four digits dialed determine the destination called.