Panasonic KX-TD500 System Reference Manual page 346

14.04 Alternate Routing
Description When more than two PBXs at different locations are interconnected with a
network of Tie Lines, your KX-TD500 works as an intermediate switching office
to other PBXs in the network by relaying tie calls from one PBX to another.
A problem of telephone switching is that blocking sometimes occurs on the
network, and a call cannot be switched as required because all the lines on a
given route are occupied or unavailable.
By utilizing this relay function, several alternative routes can be set up
beforehand in addition to the primary-route. This permits tie calls to be routed
from "A to B" or "A through C to B" and so on.
If the primary-route is poor because of equipment failure or congestion, KX-
TD500 bypasses it and selects the secondary-route.
On receipt of a tie call, KX-TD500 analyzes it to determine the destination to
which the call must be sent or the route by which the calls will be sent, and then
transmit it.
Alternate Routing makes a Tie Line network more flexible in adapting to peaks
of traffic and it provides a variety of different routing plans.
PBX-1
PBX Code: 951
TG 10
TG 11
Ext. 100
TG 11
TG 12
PBX Code: 953
PBX-3
: Primary-route
: Secondary-route
Call Flow
1.Ext.100 dials "7+952+200".
2.When "952" is found in the table, TG10 (Hunt Sequence 01 for "952")
is selected automatically.
• If TG10 is not available, TG11(Hunt Sequence 02) will be selected.
In this case, the call is sent to PBX-2 via PBX-3 and -4.
The treatment of the call is decided by Routing Table of PBX-3 and then
PBX-4.
3.The call is sent to PBX-2.
3-F-86
A Network of Tie Lines
PBX-2
PBX Code: 952
TG 10
TG 13
TG 13
TG 12
PBX Code: 954
PBX-4
Ext. 200