SIP is the protocol for connecting between studios, which has replaced ISDN.
ipDTL includes SIP calling as standard. No ISDN line required.
Two service levels are offered: Tel and Tel+. Tel allows calls to landlines and some mobiles in many countries. Tel+ also allows calls to a wider range of countries and mobiles.
Just add Tel to your ipDTL subscription.
You can also save an entry in your Destinations list. ( + )
* Note that by default, Send a Link is Auto-Accept only.
You can now connect by simply clicking it in your main Destinations list.
The Tel service is provided on a 'fair-use' basis.