Dial and Options String

The dial string of chan_misdn got more complex, because we added more features, so the generic dial string looks like:

• mISDN/<port>[:bchannel]|g:<group>/<extension>[/<OPTIONSSTRING>]
  
  The Optionsstring looks Like:
  :<optchar><optarg>:<optchar><optarg>...
  
  the ":" character is the delimiter.
  
  The available options are:
    a - Have Asterisk detect DTMF tones on called channel
    c - Make crypted outgoing call, optarg is keyindex
    d - Send display text to called phone, text is the optarg
    e - Perform echo cancelation on this channel,
        takes taps as optarg (32,64,128,256)
   e! - Disable echo cancelation on this channel
    f - Enable fax detection
    h - Make digital outgoing call
   h1 - Make HDLC mode digital outgoing call
    i - Ignore detected DTMF tones, don't signal them to Asterisk,
        they will be transported inband.
   jb - Set jitter buffer length, optarg is length
   jt - Set jitter buffer upper threshold, optarg is threshold
   jn - Disable jitter buffer
    n - Disable mISDN DSP on channel.
        Disables: echo cancel, DTMF detection, and volume control.
    p - Caller ID presentation,
        optarg is either 'allowed' or 'restricted'
    s - Send Non-inband DTMF as inband
   vr - Rx gain control, optarg is gain
   vt - Tx gain control, optarg is gain
  

chan_misdn registers a new dial plan application "misdn_set_opt" when loaded. This application takes the Optionsstring as argument. The Syntax is:

misdn_set_opt(<OPTIONSSTRING>)

When you set options in the dialstring, the options are set in the external channel. When you set options with misdn_set_opt, they are set in the current incoming channel. So if you like to use static encryption, the scenario looks as follows:

Phone1 --> * Box 1 --> PSTN_TE
PSTN_TE --> * Box 2 --> Phone2

The encryption must be done on the PSTN sides, so the dialplan on the boxes are:

* Box 1:
exten => _${CRYPT_PREFIX}X.,1,Dial(mISDN/g:outbound/:c1)

* Box 2:
exten => ${CRYPT_MSN},1,misdn_set_opt(:c1)
exten => ${CRYPT_MSN},2,dial(${PHONE2})