Delay inbound IP call answer

$inbound_delay line delayms startrange endrange

This command is used to delay the answering of an inbound call for a short period.  It is to be used when multiple nodes are registered with an ISP or PBX and only one is to answer the simultaneous calls sent to all registered nodes.  If the primary node is down, another node will then answer the call after the delay period, thus providing redundancy for call answering.  The ISP must be aware of the fact that the call has been answered by the first node and drop the call to the other node(s) when all are operational.  The Call ID SIP parameter (this is not the 'caller ID') must be common to the concurrent calls.

The parameters on this command are used as follows:

linethe line or line group affected by the command.  Normally this will be a nodename and the whole node will be affected.
delaymsthe delay period in milliseconds.  A value of 200 is recommended.  However if more than two nodes are used for this feature, they should be given slightly different delay periods, for example 190, 200, 210.
startrange, endrangethe start and end of a subrange of the range 00 to 99.  When an incoming call has a calculated value outside this range, the delay will be applied.  See the examples below.

When implemented, commands should be supplied for all nodes registered to handle inbound traffic for the same account.


Calls are answered immmediately.


BladeWare SIP, and TE Systems SIP, with an ISP or PBX which can support multiple registrations in a compatible way.  Currently we have tested this feature with BabyTel as IP provider


For two nodes:

$inbound_delay  M1  200 00 49

$inbound_delay  M2  200 50 99

For three nodes:

$inbound_delay  M1  190 00 33

$inbound_delay  M2  200 34 66

$inbound_delay  M3  210 67 99