New SIP module:

• STUN and DNS compatibility increased
• SRTP - compatibility with third party clients (v.3 SRTP worked only in iSP-to-iSP model)
• security: TLS - major bug fix
• SIP servers compatibility increased
• DTMF signalling - major bug fix

New Audio module:

• Voice delay significantly reduced
• Voice quality improved
• Noise reduction more effective
• Call transfer - reliability improved
• Audio call conference - voice quality improved, required bandwidth reduced

Calls recording:

• Implemented from scratch in version 4
• Build-in PCM-WAV high quality converter (version 3 had used external script to convert sound)
• Call recording window redesigned for ease of use

GUI lifting:

• The interface has beed redesigned to comply with the newest OS X
• More intuitive navigation
• Address Book - compatibility with El Capitan Contacts
• New fonts and graphics
• Application icon redesigned

Compatibility with OS X El Capitan