astlocal*CLI> core show channeltype IAX2
-- Info about channel driver: IAX2 --
  Device State: yes
    Indication: yes
     Transfer : yes
  Capabilities: 65535
   Digit Begin: yes
     Digit End: yes
    Send HTML : yes
 Image Support: yes
  Text Support: yes
astlocal*CLI>
astlocal*CLI> core show channeltype SIP
-- Info about channel driver: SIP --
  Device State: yes
    Indication: yes
     Transfer : yes
  Capabilities: 65535
   Digit Begin: yes
     Digit End: yes
    Send HTML : no
 Image Support: no
  Text Support: yes

  
  Connected to Asterisk 1.4.5 currently running on astlocal (pid = 4627)
Verbosity is at least 3
    -- Executing [888@default:1] Goto("SIP/91-09d6aa70", "dtmftest|s|1") in new stack
    -- Goto (dtmftest,s,1)
    -- Executing [s@dtmftest:1] Answer("SIP/91-09d6aa70", "") in new stack
    -- Executing [s@dtmftest:2] Read("SIP/91-09d6aa70", "FOO") in new stack
[Jun 22 14:40:45] DTMF[4678]: channel.c:2297 __ast_read: DTMF end '6' received on SIP/91-09d6aa70, duration 4800 ms
[Jun 22 14:40:47] DTMF[4678]: channel.c:2297 __ast_read: DTMF end '5' received on SIP/91-09d6aa70, duration 3680 ms
[Jun 22 14:40:48] DTMF[4678]: channel.c:2297 __ast_read: DTMF end '4' received on SIP/91-09d6aa70, duration 4800 ms
    -- User disconnected
  == Spawn extension (dtmftest, s, 2) exited non-zero on 'SIP/91-09d6aa70'
.....
    -- Executing [888@default:1] Goto("IAX2/MANCHESTER-2", "dtmftest|s|1") in new stack
    -- Goto (dtmftest,s,1)
    -- Executing [s@dtmftest:1] Answer("IAX2/MANCHESTER-2", "") in new stack
    -- Executing [s@dtmftest:2] Read("IAX2/MANCHESTER-2", "FOO") in new stack
[Jun 22 14:44:01] DTMF[4918]: channel.c:2297 __ast_read: DTMF end '4' received on IAX2/MANCHESTER-2, duration 0 ms
[Jun 22 14:44:03] DTMF[4918]: channel.c:2297 __ast_read: DTMF end '5' received on IAX2/MANCHESTER-2, duration 0 ms
[Jun 22 14:44:05] DTMF[4918]: channel.c:2297 __ast_read: DTMF end '6' received on IAX2/MANCHESTER-2, duration 0 ms
[Jun 22 14:44:08] DTMF[4918]: channel.c:2297 __ast_read: DTMF end '5' received on IAX2/MANCHESTER-2, duration 0 ms
    -- User entered '4565'

This is the sip.conf entry:

[general]
context=default
insecure=very

[91]
type=friend
qualify=yes
context=default
callerid=91
host=dynamic
canreinvite=no
dtmfmode=rfc283
call-limit=1
rfc2833compensate=yes