[incoming-fwd]
exten => 536177,1,Answer()
exten => 536177,2,Background(transfer)
exten => 536177,3,Dial(${SPAP1},60,TtH)
exten => 536177,4,Hangup()

exten => 0,1,Dial(${SPAP2},30)
exten => 0,2,Hangup()

SPAP1 is the SIP id for port 1 on the SPA-2000
SPAP2 is the SIP id for port 2 on the SPA-2000