SvxLink is a project that develops software targeting the ham radio community. It started out as an EchoLink application for Linux back in 2003 but has now evolved to be something much more advanced. It is a project of Tobias Blomberg SM0SVX. 
The SvxLink Server is a general purpose voice services system, which when connected to a transceiver, can act as both an advanced repeater system and can also operate on a simplex channel. One could call it a radio operating system since it sits between the hardware (transceiver) and the applications (modules) and handle basic system services as well as input and output.
SvxLink is very extensible and modular. Voice services are implemented as modules which are isolated from each other. Modules can be implemented in either C++ or TCL. Examples of modules are:
- Help — A help system
- Parrot — Play back everything that is received
- EchoLink — Connect to other EchoLink stations
- DtmfRepeater — Repeater received DTMF digits
- TclVoiceMail — Send voice mail to other local users
- PropagationMonitor — Announce propagation warnings from dxmaps.com
- SelCall — Send selective calling sequences by entering DTMF codes
Qtel, the Qt EchoLink client, is a graphical application used to access the EchoLink network.
SvxLink worked at Raspberry Pi (Thanks VR2XKP)
Features of the SvxLink server:
These are the most important features of the SvxLink server application.
- Can act as a repeater controller or just operate on a simplex channel
- Plugin based system to load voice services into the SvxLink logic core
- DTMF controlled
- DTMF anti-flutter mode to suppress multiple digit detection when mobile flutter is present or during weak-signal conditions
- A sound clip based system for announcements
- Periodic identification
- A script based (TCL) event handling system
- Possible to use left/right stereo channels as two mono channels
- Roger beep
- Trigger manual identification by pressing DTMF *
- A simple shortcut, or macro, subsystem
- Repeater logic specific features:
- Multiple repeater activation modes: 1750 Hz tone burst, CTCSS, DTMF or squelch open.
- The repeater can be configured to activate again on just squelch open directly after close.
- Periodic “idle sound” when the repeater is up but no signal is being received
- Announcements are mixed in with normal audio
- The volume of announcements is lowered if there are other traffic
- Remind users to identify themselves if they don’t
- Possible to define multiple logic cores to connect to multiple transceivers
- Possible to link logic cores together
- Support for multiple receivers using a software voter
- Remote receivers can be linked to the logic core via TCP/IP(Internet)
- Remote transmitters can be linked to the logic core via TCP/IP (Internet)
- Multiple squelch detectors: Vox, CTCSS, signal level, evdev (/dev/input/) and external (through serial port pin)
- Multi tone signalling to transmit signal strength measurements from a remote RX site that is linked in through RF.
- Digital deemphasis/preemphasis filter
- DTMF muting
- Squelch tail elimination
- Flexible CTCSS transmit. A tone can be configured to be transmitted always or on specific events like when the squelch is open, another logic core transmits, a module transmits and/or when an announcement is being played.
- A QSO recorder feature to record QSO:s to WAV-files.
- Possible to control SvxLink using selective calling (SelCall) codes in addition to DTMF commands.
- A simple help system module
- A parrot module that retransmit received audio
- An EchoLink module used to connect to other EchoLink nodes
- Idle timeout
- A callsign lookup/connect by callsign function
- List connected stations on demand
- Own node id report function
- Random connect to link, repeater or conference
- Reconnect to last disconnected node
- Listen only mode
- APRS node info announcement support
- If two SvxLink nodes connect, a better audio codec, Speex, is used instead of the GSM codec. This will provide much improved audio quality.
- Possible to limit both incoming and outgoing connections to specified stations using regular expressions
- EchoLink Proxy support
- A voice mail module
- Record voice mail for local users
- A DTMF repeater module that retransmits received DTMF digits.
- Control other DTMF controlled stations on the same frequency
- A propagation monitor module that read back propagation warnings from DXMAPS (www.dxmaps.com) alert emails.
- A selective calling encoder module that use DTMF commands to make SvxLink send out selective calling sequences.
- Possible to write new modules in the TCL scripting language
Qtel – The Qt EchoLink Client
These are the most important features of the Qtel application.
- Graphical EchoLink client application
- Use the Qt widget toolkit
- The EchoLink station list is divided into Conferences, Links, Repeaters and Stations
- A bookmark system
- Support for multiple languages (English, Swedish, German, Spanish, Ukranian, Russian, Hungarian, Japanese, French and Italian at the moment)
- VOX
- When connecting to a SvxLink node through EchoLink, a better audio codec, Speex, is used. This provides a much improved audio quality.
- EchoLink Proxy support
Info at www.svxlink.org
