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Note that OpenZAP has been superseded by FreeTDM. OpenZAP development is stalled and no new features will be developed. Use FreeTDM instead.

This page is kept only for historical purposes. If you are using OpenZAP then please update to FreeTDM. If you have not yet started using a TDM card yet then go straight to FreeTDM.

OpenZAP is a library used by FreeSWITCH's to interface to Sangoma, DAHDI and PIKA boards. OpenZap implements a TDM unified abstraction for both signaling (PRI, BRI, SS7, MFC-R2 etc) and board I/O APIs (Sangoma TDM API, DAHDI, PIKA etc). Depending on your hardware requirements, the proper drivers are still needed. If you have Sangoma boards you must install the wanpipe drivers first, OpenZAP then will use the drivers to communicate to Sangoma boards. The same apply for other board APIs like Zaptel/DAHDI.

OpenZAP also offers services like DTMF detection to its user applications (in most cases FreeSWITCH).




  • Development is finished and testers are currently wanted.
  • So far we have analog (only tested in US so far but we are working on UK too) and Q.931 PRI signaling but we should be able to add more things like RBS as time progresses.
  • The PRI stack is incomplete.
  • MFC/R2 support has been added using the OpenR2 signaling library but still needs stress testing.




Zaptel is actually a decendant of the original public domain tormenta driver made by Jim Dixon in 2000.

Our goal here is to pick up where this left off and keep the important functionality in the driver and the rest in user space. Eventually we hope to make our own platform-agnostic driver interface.


We only use zaptel as a device via the socket opened on the operating system to access the low level features such as open close read write and the rest of the functionality is implemented in our own user space layer.

For clarification -- we simply speak to the zaptel kernel interface. In fact, we don't even use their header files to build. So if you have a card that requires modified drivers, then you would need to use those, but they should work as long as they maintain the same zaptel interface.


Hardware/Driver compatibility

OpenZAP should work with the latest Sangoma TDM API as well as any Zaptel dating back to when there was only Tormenta 2.

The hardware support thus far includes Zaptel and native Sangoma TDM API. The existing codebase includes mod_openzap for FreeSWITCH that is currently functional with analog and Euro or DMS100 PRI.

Rhino Cards: Rhino cards use Zaptel, however there are some caveats. Please see the Rhino page for details.

R2 Support: Moises Silva has added preliminary support for R2. Please see the OpenZAP_OpenR2 page for details.

FXO/FXS Terminology

A port that connects to a telephone line is an FXO port. If you use zaptel, you configure the port as an FXO port in zaptel.cfg. The port uses FXS signalling, so you configure OpenZAP in openzap.conf to use FXS signalling for the same port.

A port that connects to a telephone extension is an FXS port. If you use zaptel, you configure the port as an FXS port in zaptel.cfg. The port uses FXO signalling, so you configure OpenZAP in openzap.conf to use FXS signalling for the same port.

To summarize:

usage type / zaptel.cfg signalling / openzap.cfg
telephone line FXO FXS
telephone extension FXS FXO

Setup hardware drivers

OpenZAP can be used in two modes. See the diagram (above). The first mode uses Zaptel and will let you use any card Zaptel supports. The other mode is wanpipe, which will let you interact directly with Sangoma cards without going through Zaptel. The hardware drivers only need to be configured if you are using the first mode. If you are using wanpipe, then skip this step.

A set of step-by-step instructions is available on the Zaptel Tutorial page.

You must have the Zaptel API up and running in order to use the OpenZap module.

The hardware you intend to use, e.g., an FXO/FXS card or a PRI card, should be installed first so you can verify the zaptel installation after it's been completed. (Make sure the system has internet connectivity as it downloads some utilities)

At this point we can follow two different paths: general instruction and Debian instructions.

Non-Debian Instructions

Note in this example, channel 1 is connected to the telephone line (FXO), and channel 4 is connected to a telephone extension (FXS).

1. Download the zaptel-1.4.2.tar.gz from reliable sources. Untar the source tarball, compile and install it.

# I had to rely on this older zaptel version that works for me, as the newer ones were troubling me.
$ tar -zxvf zaptel-1.4.2.tar.gz
$ cd zaptel-1.4.2
$ ./configure
$ make
$ make install
$ make config

2. Make sure you have the proper zaptel.conf in your /etc directory

3. Be cautious while configuring country zone in zaptel.conf at /etc. For India, e.g.,

 ----- @/etc/zaptel.conf -----

4. Add the wctdm and zaptel modules now.

$ modprobe wctdm
$ modprobe zaptel

5. Now verify the installation with the ztcfg command

$ ztcfg -vv
Zaptel Version: 1.4.2
Echo Canceller: MG2
Channel map:
Channel 01: FXO Kewlstart (Default) (Slaves: 01)
Channel 04: FXS Kewlstart (Default) (Slaves: 04)
2 channels configured.

Debian Instructions

Debian makes this entire process rather easy.

1. Install the zaptel and zaptel-source package by using your favorite package management tool, e.g., apt-get or aptitude.

2. Build the zaptel-source package and create a deb which contains the Zaptel kernel modules:

$ module-assistant prepare
$ module-assistant build zaptel-source

You may wish to example the Debian-specific README files provided by the zaptel (not the zaptel-source) package.

3. Install the deb created in the previous step, which is likely found at /usr/src.

4. Create the /etc/zaptel.conf file. The easiest way to do this is with genzaptelconf:

genzaptelconf -vsdM

(Note: If genzaptelconf cannot "find" the hardware, you may have to use modprobe to load the wctdm or zaptel kernel modules, or perhaps both.)

genzaptelconf may complain about some obscure program named "asterisk" not being present on your system. Regardless, /etc/zaptel.conf will be created.

5. Configure the board:


6. check to see the board's status:


Your installation is up and running. At next boot, if you use udev, your hardware will be detected automatically and the system will load the Zaptel modules and configure the hardware from the /etc/zaptel.conf file.

Use outside North America

If you are using zaptel cards outside North America (e.g. Australia) you may have to specify the operating country when the module loads. Just specifying the zone in zaptel.cfg is not sufficient. In Debian Lenny I configure mine to use the Australian standards mode by putting the following line in /etc/modprobe.d/zaptel.

options wctdm opermode=AUSTRALIA

At boot I see messages like:

Boosting ringer on slot 1 (89V peak)
Module 0: Installed -- AUTO FXS/DPO
Boosting ringer on slot 2 (89V peak)
Module 1: Installed -- AUTO FXS/DPO
Module 2: Installed -- AUTO FXO (AUSTRALIA mode)
Module 3: Installed -- AUTO FXO (AUSTRALIA mode)
Found a Wildcard TDM: Wildcard TDM400P REV I (4 modules)


OpenZAP Download

mod_openzap is now included with Git clone of FreeSWITCH under libs/open_zap. Therefore, you do not have to download the svn.

However, if you have not checked out FreeSWITCH and would like to look at the OpenZAP code, you can browse the OpenZAP source code here or

Download via subversion:

Type This
svn co openzap_trunk

Adding libpri Support

OpenZAP has its own PRI stack that might do everything you require. However, it is still in development. If you would like to use libpri as the PRI stack within OpenZAP, install libpri and compile OpenZAP to use it.

Download and install libpri:

Type This
cd /usr/src
tar -zxvf libpri-1.4-current.tar.gz
cd libpri-1.4.X
make && make install

Note: replace 'X' with the correct release number. As of this writing, libpri-1.4.10 is the latest version.

When you load mod_openzap, if you're getting an error stating that is missing (or whatever version you've compiled), it may be because the LD_LIBRARY_PATH isn't set up correctly. Be sure /usr/lib is included in the LD_LIBRARY_PATH environment variable when you start FS. Consider adding it to /etc/init.d/freeswitch if it's not already there.

OpenZAP Compilation

1. Make sure while compiling FreeSWITCH source, you have included ../../libs/openzap/mod_openzap in modules.conf (just need to uncomment it)

2. Tones should be configured in OpenZAP and not in zaptel. FreeSWITCH uses its libteletone for tones generation and detection, and does not rely on zaptel tones configuration. Therefore it does not matter which country zone is configured in zaptel. Make sure that you have loaded your country-specific tones at /etc/openzap/tones.conf. Check for your country-specific dial-tone/ring-tone/busy-tone etc in tones.conf because you can't make outbound calls on FXO unless you have proper tones configured.For eg, the tones.conf(India) will look like this tones.conf Example

NOTE: By default, tones.conf for USA is available at ${freeswitch_src}/libs/openzap/conf/ , For the new versions, it's installed under ${prefix}/conf/tones.conf

3. If you are using libpri (as per previous step), re-configure OpenZAP to use libpri:

Type This
./configure --with-libpri
make mod_openzap-install

Configuration Files

Depending upon your specific hardware there are several configuration files. The two primary files are openzap.conf (located in the conf directory) and openzap.conf.xml (located in conf/autoload_configs directory).

In a typical zaptel-based installation, the openzap.conf file will mirror the contents of the zaptel.conf file. The openzap.conf file has several configuration options:

  • name - default caller ID name for this span
  • number - default caller ID number for this span
  • trunk_type - trunk type, i.e. t1, e1, etc.
  • b-channel - specify one or more b-channels (ISDN)
  • d-channel - specify one or more d-channels (ISDN)
  • fxo-channel - specify one or more FXO channels (analog, RBS)
  • fxs-channel - specify one or more FXS channels (analog, RBS)

Note for the fxo/fxs settings you specify what signalling is used. This is typically the opposite of the type of port which you specified (if applicable) in zaptel.cfg.

See the openzap.conf_Examples page for some typical setup examples.

The openzap.conf.xml contains the higher layer configuration information for the span(s) that are described in openzap.conf. The openzap.conf.xml file defines a span as analog or PRI. For PRI spans, the dialect type is also specified here.

See the openzap.conf.xml_Examples page for some typical setup examples.

NOTE: The new OpenZAP install process will now put the appropriate conf files in ${prefix}/conf/openzap.conf and will put openzap.conf.xml in ${prefix}/conf/autoload-configs/ This is different from the old process. openzap.conf is now located at ${prefix}/conf/openzap.conf and is no longer needed in /etc/openzap.

Zaptel mode

to be written

Wanpipe mode

In this mode you do not need to have Zaptel installed. You will a recent version of Wanpipe (3.5.10 works) and compile it in TDM Voice API mode. For an E1 span the openzap.conf file will look like this, where the SPAN is put in Wanpipe mode by specifying span wanpipe

The examples page shows how to configure PRI spans to use libpri.

[span wanpipe PRI_1]
number => 1
trunk_type => e1
b-channel => 1:1-15
d-channel => 1:16
b-channel => 1:17-31

A T1 span would look more like this:

[span wanpipe PRI_1]
number => 1
trunk_type => t1
b-channel => 1:1-23
d-channel => 1:24

/etc/wanpipe/wanpipe1.conf will look like this:

wanpipe1 = WAN_AFT_TE1, Comment

w1g1 = wanpipe1, , TDM_VOICE_API, Comment

S514CPU         = A
CommPort        = PRI
PCISLOT         = 4
PCIBUS          = 13
FE_MEDIA        = E1
FE_LCODE        = HDB3
FE_FRAME        = CRC4
FE_LINE         = 1
LBO             = 120OH
MTU             = 1500
UDPPORT         = 9000
TTL             = 255
TDMV_SPAN       = 1
TDMV_DCHAN      = 16

MTU             = 80

Only spans configured as TDM_VOICE_API in wanpipe*.conf can be used together with a SPAN configured as wanpipe in openzap.conf

The autoload_configs/openzap.conf.xml will then look like this:

<configuration name="openzap.conf" description="OpenZAP Configuration">
    <param name="debug" value="0"/>
    <!--<param name="hold-music" value="$${moh_uri}"/>-->
    <!--<param name="enable-analog-option" value="call-swap"/>-->
    <!--<param name="enable-analog-option" value="3-way"/>-->
     <span name="PRI_1">
       <!-- Log Levels: none, alert, crit, err, warning, notice, info, debug -->
       <param name="q921loglevel" value="alert"/>
       <param name="q931loglevel" value="alert"/>
       <param name="mode" value="user"/>
       <param name="dialect" value="q931"/>
       <param name="dialplan" value="XML"/>
       <param name="context" value="pstn"/>

If Wanrouter has been brought up by doing /etc/init.d/wanrouter start and you now start FreeSWITCH the span should come up and you can now hopefully dial out using

 <extension name="outgoing-pri">
  <condition field="destination_number" expression="^.+$">
    <action application="bridge" data="openzap/1/a/${destination_number}"/>

Make sure you give access rights to /dev/wptdm* for FreeSWITCH user in case you are running as non-root user. You can make it with putting:

SUBSYSTEM=="wptdm", OWNER="freeswitch", GROUP="freeswitch", MODE="0660"

into /etc/udev/rules.d/wanpipe.rules and restarting the udev service.

You may also need to add the following to /etc/udev/rules.d/wanpipe.rules:

SUBSYSTEM=="wanpipe", OWNER="freeswitch", GROUP="freeswitch", MODE="0660"

The Boost PRI stack groups together all channels from all spans into a single logical span. You may still dial a specific span by using the group nomenclature. <STUB, more to come when I get a sec to track it all down...>


As an example, let's see configuration for OpenZap module with Digium TDM400P 2FXS/2FXO card. Configuration OpenZAP- DigiumTDM400P Example

Tormenta2: Openzap.conf Examples and Openzap.conf.xml Examples. You will also need a zaptel.conf, since it is tied in with ztcfg into the kernel module configs.

Here's a step-by-step for installing and configuring a Sangoma A101DE card with libpri configured for T1/NI2.

Start Up FreeSWITCH

1. Once you are done with installing zaptel drivers and fixed the FXS/FXO card on your machine, the green LEDs(Digium TDM400 card in my case) on your card will start glowing. (that's good omen for you :-) )

2. At the time of running FreeSWITCH from /usr/local/freeswitch/bin/, make sure again that <load module ="mod_openzap"/> is included in /usr/local/freeswitch/conf/autoload_configs/modules.conf.xml

3. Make sure you see the OpenZAP FXS and FXO configuration messages on your console when you run FreeSWITCH. For example,

2008-05-01 18:10:32 [INFO] zap_zt.c:170 zt_open_range() configuring device /dev/zap/channel channel 1 as OpenZAP  device 1:1 fd:33
2008-05-01 18:10:32 [INFO] zap_zt.c:170 zt_open_range() configuring device /dev/zap/channel channel 4 as OpenZAP device 2:1 fd:34
2008-05-01 18:10:32 [INFO] zap_io.c:1978 load_config() Configured 2 channel(s)
2008-05-01 18:10:32 [CONSOLE] switch_loadable_module.c:749 switch_loadable_module_load_file() Successfully Loaded [mod_openzap]
2008-05-01 18:10:32 [NOTICE] switch_loadable_module.c:139 switch_loadable_module_process() Adding Endpoint 'openzap'
2008-05-01 18:10:32 [NOTICE] switch_loadable_module.c:245 switch_loadable_module_process() Adding API Function 'oz'
For digital channels like PRI's the messages will be similar:

2008-09-26 10:55:26 [INFO] zap_io.c:2213 zap_load_module() Loading IO from /usr/local/freeswitch/mod/
2008-09-26 10:55:26 [INFO] zap_io.c:2006 load_config() auto-loaded 'zt'
2008-09-26 10:55:26 [INFO] ozmod_zt.c:170 zt_open_range() configuring device /dev/zap/channel channel 1 as OpenZAP device 1:1 fd:50
2008-09-26 10:55:26 [INFO] ozmod_zt.c:170 zt_open_range() configuring device /dev/zap/channel channel 2 as OpenZAP device 1:2 fd:51
2008-09-26 10:55:26 [INFO] ozmod_zt.c:170 zt_open_range() configuring device /dev/zap/channel channel 3 as OpenZAP device 1:3 fd:52
2008-09-26 10:55:26 [INFO] ozmod_zt.c:170 zt_open_range() configuring device /dev/zap/channel channel 96 as OpenZAP device 4:24 fd:144
2008-09-26 10:55:26 [INFO] zap_io.c:2137 load_config() Configured 96 channel(s)
2008-09-26 10:55:27 [INFO] zap_io.c:2230 zap_load_module() Loading SIG from /usr/local/freeswitch/mod/
2008-09-26 10:55:27 [INFO] zap_io.c:2346 zap_configure_span() auto-loaded 'isdn'
2008-09-26 10:55:27 [CONSOLE] switch_loadable_module.c:789 switch_loadable_module_load_file() Successfully Loaded [mod_openzap]

4. Now you can take a ride on your Ozzzzzzz... zip zap zoom ;)

OpenZAP CLI Commands

To see a list of your configured spans, at the CLI type

oz list

To see detailed information about a specific span type

oz dump <span_id> [<chan_id>]

To save Q.931 packets in a *.pcap file for decoding in wireshark

oz q931_pcap <span_id> on|off [pcapfilename without suffix]
Informational Tip

Note: Only if you have libpcap and libpcap-devel installed on your system! Also note that you can't use libpri if you want to be able to capture the q931 traffic, it only works with ozmod_isdn.


To see debug messaging if you are using libpri

oz libpri debug <span_id> all

To turn off the debug messaging if you are using libpri

oz libpri debug <span_id> off

Sangoma's wanpipemon utility is handy for generating pcap files on the d-channel of a PRI circuit. Check out Sangoma's wiki entry for more information.

Dialplan Configuration

Channel Variables

  • openzap_span_number
OpenZAP span number
  • openzap_chan_number
OpenZAP channel number


The syntax of the bridge application data's option is openzap/span/port/phone-number.
To automatically discover of a free port number instead of a number you can use "a" or "A". For example, "openzap/1/a/123456789" will pick up the first available port in span 1 to dial the number 123456789.
Using "A" for the port will find the highest-numbered port available.


1. To bridge an inbound call to your FXS that is configured on channel 1, for an UA registered as configure as below

 <extension name="incoming-fxs">
   <condition field="destination_number" expression="^(507)$">
     <action application="bridge" data="openzap/1/1"/>

2. To bridge an outbound call onto your FXO card that is configured on channel 4, for any 10-digit destination configure as below

 <extension name="outgoing-fxo">
   <condition field="destination_number" expression="^(\d{10})$">
     <action application="bridge" data="openzap/2/1/${dialed_ext}"/>

3. To bridge an outbound call to the first available port from a dual-span PRI card, regardless of the span number (will try the 1st span first, then the 2nd span if the 1st one is not available):

 <extension name="outgoing-pri">
   <condition field="destination_number" expression="^(\d{10})$">
     <action application="bridge" data="openzap/1/a/$1|openzap/2/a/$1"/>

4. To bridge about outbound call to the last available channel on a PRI span:

 <extension name="outgoing-pri">
   <condition field="destination_number" expression="^(\d{10})$">
     <action application="bridge" data="openzap/1/A/$1"/>

Debugging your OpenZAP set up

Symptom: "Why bother changing state on 1:1 from UP to UP" or "Cannot get a RING_START event on a non-fxo channel"

Resolution: The problem here is that you have your channel that connects to the telco defined as an fxs channel, instead of an fxo channel. Note that the other guys ask you to specify what kind of signalling the channel is expecting at the other end, while FreeSWITCH wants you to specify what type of signalling the FreeSWITCH end is.

To fix this, change your openzap.conf to something similar to.

 [span zt]
 name => OpenZAP
 number => 1
 fxo-channel => 1

Your zaptel.conf still requires you to specify what sort of signalling you are expecting to see on the other end so it will look like.


Symptom: [ERR] ozmod_wanpipe.c:440 wp_open_range() failure configuring device s*c** using a Sangoma card with FreeSWITCH running as a normal user

Use UDEV to set the right permissions. Create an file called /etc/udev/rules.d/wanpipe.rules with the following line (replace freeswitch with your actual user):

 SUBSYSTEM=="wptdm", OWNER="freeswitch", GROUP="freeswitch", MODE="0660"

Then reload your udev by doing /etc/init.d/udev reload or restarting your system and reload your wanpipe, The permissions should now be correct. CentOs I use start_udev

Symptom: Signalling works but buzzing audio is heard using Wanpipe on a 64 bit system with > 4 GB RAM

Recompile wanpipe with ./Setup install --64bit_4GB


Q: OpenZAP vs. mod_wanpipe

OpenZAP replaces mod_wanpipe

Q: OpenZAP vs. libpri

OpenZAP can replace libpri or can be used with libpri. Because OpenZAP is licensed under the BSD it is actually compatible with the GPL-licensed libpri. See OpenZAP#Adding_libpri_Support for setup instructions.

Q: Does OpenZAP support libss7?

Currently we do not have any open source SS7 solutions but commercial options are available.

Q: How do I configure spanmaps?

This can be done in the autoload_configs/openzap.conf.xml file.

Q: Do you need a special tor2.c for using Tormenta2?

You should not need anything special, just zaptel loaded with any plugin tor2, whatever. Any variation of the driver should be fine since zaptel is fairly generic. Tormenta2 clones from are reported to work well.

Q: For analog cards (XP100), will I need zaptel kernel drivers?

Yes, for analog cards, OpenZAP communicates w/ the zaptel kernel drivers via sockets, which in turn communicates with the hardware card.

Q: How do I send a hook flash?

Use the send_dtmf app to send F like this:

<action application="send_dtmf" data="F"/>

Q: If I want Sangoma with OpenZAP, do I need wanpipe installed?


Sangoma cards can be used in two ways with OpenZAP depending on the driver set in FS_ROOT_DIR/conf/openzap.conf

  • Using the wanpipe driver if the span is configured as TDM_VOICE_API in the Wanrouter setup script.
  • Using the zaptel or DAHDI driver if the span is configured as TDM_VOICE in Wanrouter setup script.

wanpipe is preferred, but if you need to use things like OSLEC operating in the zaptel/DAHDI driver you will need to use the second option.

Q: Does OpenZAP support ccs, hdb3 with Digium te420?

Yes, also CAS is supported in MFC-R2 or DTMF-R2 lines.

Q: Does OpenZAP support EuroISDN?

Yes, via libpri, sangoma prid, and to some extent via the openzap pri stack. FreeTDM should have full support when we re-enable our native isdn stack, but you can use via the other stacks already.

Q: I hear some line noise on analog card

FreeSWITCH/OpenZAP (in opposition to Asterisk/ZAPATA) doesn't implement it's own echo canceller in software. If you are hearing strange noise on analog card without hardware echo cancellation, try to apply separate echo canceller - e.g. OSLEC.

Q: Does OpenZAP support OSLEC?

Yes. OSLEC operates at the Zaptel driver level so no special OpenZAP configuration is needed. Just load OSLEC and go!


See Zapata_zaptel_interface.

See Also

  • World Tone Database: [1]
  • ITU World Tone List: [2]