Here you will find the list of Free VoIP Gatways that you can use to connect the VoIP network to your public telephone network (PSTN). In this way, you can make calls and receive them, from your PTSN, even if you are using an IP-based system, just like your traditional phone.
Here are the List of Free VoIP gateways that you can use at your home or business place:
isdn2h323 is a Linux based H.323 - ISDN gateway.
1. ISDN and H.323 users can initiate a connection.
2. The number of simultaneous incoming and outgoing calls is limited by the number of available ISDN channels only.
3. H.323 users can specify the ISDN number of the other party.
4. The gateway's administrator can assign an ISDN MSN to a H.323 user. This makes it possible for an ISDN user to call a H.323 user directly. The gateway will choose the H.323 user id depending on the called ISDN MSN.
5. The gateway discovers an available H.323 gatekeeper and registers with the gatekeeper. It's possible to specify one or more phone prefixes the gateway is responsible for.
6. ISDN's touch-tones (DTMF) are translated to H.323's user input messages and vice versa.
7. Automatic gain control (AGC)
8. Automatic echo compensation (AEC)
9. To avoid security problems the gateway offers an option to restrict the IPs allowed to use the gateway for an outgoing ISDN call.
10.The status of the lines and the configuration of the gateway are written to a HTML file.
11. Errors and some other informations are logged using Linux's syslog() feature.
12. Three H.323 codecs are supported: ALaw, muLaw, and GSM.
13. Least Cost Router
A 4/8/12/16 port Voice Over IP (VOIP) gateway running H323, using GSM speech compression. This software enables a VOIP gateway to be built for the price of a PC and a OpenLine card. The project uses the OpenH323 PSTNGW software package. Illustration (thanks to Rodney Machado for the illustration).
New A pstngw-patch package has been developed by Voicetronix to make building the gateway software easier. It is no longer necessary to use OpenH323 CVS to check out the software. See ReadMe.txt in the pstngw-patch package for more information.
SIPRG (SIP Residential Gateway)
The SIP Residential Gateway (SIPRG) is an open source application based on the Session Initiation Protocol (SIP). The SIPRG is an IP Telephony Gateway that allows a SIP User Agent to make and receive calls between the Public Switched Telephone Network (PSTN) and a SIP-based network such as VOCAL.
The SIPRG was developed with the VOVIDA SIP stack version 1.3.0, and uses a QuickNet LineJACK card (www.quicknet.com) for connecting an Analog telephone line. Currently, it supports only a single LineJACK card and is therefore a single-line gateway.