DISA - Direct Inward Subscriber Access is not a Panasonic System but rather a Feature of many telephone systems.
Siemens/Unify/AtoS systems of course also can do DISA - a small setup would use Xpressions voicemail or similar to acheive such a thing but larger sites would have a dedicated server for same.
Extract:
DISA: Direct Inward System Access
DISA is a relatively new feature of Business Telephone Systems (PBX systems)
You must have heard many a times when you call a Business or an oraganisation, an automated message asking you to dial a digit to access a particular person &/or a department,
Press 1 for Sales department, press 2 for customer service, press 3 for support, or else wait for your call to be attended by the next available operator.
This is it - this feature in the PBX System is called DISA
Most of the digital & VoIP PBX Systems have built-in DISA.
A few analog PBX Systems & the earlier generation systems need an optional Card to go DISA.
Usually DISA also works as a TEL/FAX Autoswitch, to automatically distinguish the Fax or Phone call & send the incoming call to the desired extension. The fax is received automatically silently or maybe with a couple of ring tones in the fax machine (configurable).
Optional DISA Cards for Panasonic PBX Systems
