Someone

#--------------------------
# Start /etc/zaptel.conf
loadzone=us
defaultzone=us

# Digium Wildcard TDM04B (POTS to PSTN [Zap/g1])
fxsks=1-4

# Sangoma A102 port 1 (T1 to stations [Zap/g2])
span=1,0,0,esf,b8zs
fxoks=5-28

# Sangoma A102 port 2 (T1 to PSTN [Zap/g3])
span=1,2,0,esf,b8zs
e&m=29-52
# End /etc/zaptel.conf
#--------------------------

#--------------------------
# Start /etc/asterisk/zapata.conf
[trunkgroups]
; Wildcard TDM04B (inbound / outbound POTS to PSTN)
  signalling=fxs_ks
  context=from-external
  echocancel=yes
  echocancelwhenbridged=yes
  busydetect=yes
  musiconhold=default
  group=1
  channel => 1-4
  callprogress=no

; Sangoma A102 port 1 (internal T1 to stations)
  context=from-internal
  group=2
  signalling=fxo_ks
  channel => 5-28

; Sangoma A102 port 2 (outbound T1 to PSTN)
  context=from-internal
  group=3
  signalling=e&m
  channel => 29-52

[channels]
 context=default
 usecallerid=yes
 hidecallerid=no
 callwaiting=yes
 usecallingpres=yes
 callwaitingcallerid=yes
 threewaycalling=yes
 transfer=yes
 canpark=yes
 cancallforward=yes
 callreturn=yes
 echocancel=yes
 echocancelwhenbridged=yes
 rxgain=0.0
 txgain=0.0
 group=0
 callgroup=1
 pickupgroup=1
 immediate=no
# End /etc/asterisk/zapata.conf
#---------------------------------

#---------------------------------------------------
# Relevant part of /etc/asterisk/extensions.conf
[from-internal]
        exten => _77XX,1,NoOp(Finding channel for local exten ${EXTEN})
        exten => _77XX,n,Set(channel=$[ ${EXTEN} - 7695 ])
        exten => _77XX,n,NoOp(Calling ${EXTEN} on channel Zap/${channel})
        exten => _77XX,n,Macro(stdexten|${EXTEN}|Zap/${channel})
        exten => _77XX,n,Hangup
[macro-stdexten]
        ; Standard extension macro:
        ;   ${ARG1} - Extension  (we could have used ${MACRO_EXTEN} here as well
        ;   ${ARG2} - Device(s) to ring

        exten => s,1,Dial(${ARG2},20)
        exten => s,2,Goto(s-${DIALSTATUS},1)

        exten => s-NOANSWER,1,Voicemail(u${ARG1})
        exten => s-NOANSWER,n,Playback(vm-goodbye)
        exten => s-NOANSWER,n,Hangup

        exten => s-BUSY,1,Voicemail(b${ARG1})
        exten => s-BUSY,n,Playback(vm-goodbye)
        exten => s-BUSY,n,Hangup

        exten => _s-.,1,Goto(s-NOANSWER,1)

        exten => a,1,VoicemailMain(${ARG1})
        exten => a,n,Playback(vm-goodbye)
        exten => a,n,Hangup
# End relevant part of /etc/asterisk/extensions.conf
#---------------------------------------------------

#----------------------------------------------
# What happens when you try calling Zap/5
*CLI> dial 7700@from-internal
[Jul 10 20:39:45]     -- Executing NoOp("OSS/dsp", "Finding channel for local exten 7700") in new stack
[Jul 10 20:39:45]     -- Executing Set("OSS/dsp", "channel=5") in new stack
[Jul 10 20:39:45]     -- Executing NoOp("OSS/dsp", "Calling 7700 on channel Zap/5") in new stack
[Jul 10 20:39:45]     -- Executing Macro("OSS/dsp", "stdexten|7700|Zap/5") in new stack
[Jul 10 20:39:45]     -- Executing Dial("OSS/dsp", "Zap/5|20") in new stack
[Jul 10 20:39:45] NOTICE[8299]: app_dial.c:1079 dial_exec_full: Unable to create channel of type 'Zap' (cause 34 - Circuit/channel congestion)
[Jul 10 20:39:45]   == Everyone is busy/congested at this time (1:0/1/0)
[Jul 10 20:39:45]     -- Executing Goto("OSS/dsp", "s-CONGESTION|1") in new stack
[Jul 10 20:39:45]     -- Goto (macro-stdexten,s-CONGESTION,1)
[Jul 10 20:39:45]     -- Executing Goto("OSS/dsp", "s-NOANSWER|1") in new stack
[Jul 10 20:39:45]     -- Goto (macro-stdexten,s-NOANSWER,1)
[Jul 10 20:39:45]     -- Executing VoiceMail("OSS/dsp", "u7700") in new stack
# End of what happens when you try calling Zap/5
#------------------------------------------------