wait-ack in emi2

In the emi2 protocol, what is the lowest possible value for wait-ack? I 
am using kannel 1.2.1, and the lowest I've been able to set it to is 30. 
Anything below 30, the bearerbox would not start.

2003-05-09 14:49:47 [0] ERROR: EMI2[globe]: 'wait-ack' invalid in emi2 
configuration.
2003-05-09 14:49:47 [0] ERROR: EMI2[globe]: Failed to create emi2 smsc 
connection
2003-05-09 14:49:47 [0] PANIC: gwlib/octstr.c:2132: seems_valid_real: 
Assertion `ostr->len + 1 <= ostr->size' failed. (Called from 
gw/smsc/smsc_emi2.c:1695:smsc_emi2_create.)


--Paul