2 call appearances (lines)

Multiple active call identities

Custom ring tones

Call Waiting

Call Hold

3-way conference calling

Mute

Call redirection on demand

Call redirection unconditional

Call redirection when busy

Call redirection no answer

Reject call redirection request

Blind call transfer

Call transfer with consultation (attended call transfer)

Reject call transfer request

Call reject

Repeat last call

Do not disturb

Auto answer

Message Waiting Inidication

Voice mail speed dial

User defineable scripts triggered on call events

E.g. to implement selective call reject or distinctive ringing

RFC 2833 DTMF events

Inband DTMF

Out-of-band DTMF (SIP INFO)

STUN support for NAT traversal

Send NAT keep alive packets when using STUN

NAT traversal through static provisioning

Persistent TCP connections for NAT traversal

Missed call indication

History of call detail records for incoming, outgoing, successful and missed calls

DNS SRV support

Automatic failover to an alternate server if a server is unavailable

Other programs can originate a SIP call via Twinkle, e.g. call from address book

System tray icon

System tray menu to quickly originate and answer calls while Twinkle stays hidden

User defineable number conversion rules

Simple address book

Support for UDP and TCP as transport for SIP

Presence

Instant messaging

Simple file transfer with instant message

Instant message composition indication

Command line interface (CLI)