Q: Can the ITC- 420 handle more than 4 lines?
A: Yes. Each phone physically accommodates 4 lines; however, the ITC- 420 gives your office the flexibility to handle more than 4 total incoming lines. Line 1 must all be shared with all phones on the network. This is in order for the phones to communicate to each other i.e. call transfer, intercom etc. Then you can have each phone with its OWN 3 lines; or share any combination of lines.
Say you have 6 phones in your office. You can each share line 1, 2, and 3; and everyone has their own private line. Thus, the total number of lines = 3 shared lines + 6 (one dedicated line per phone x 6 phones) = 9 separate lines.
Here's another way many doctors configure their ITC- 420
1) All phones share line 1
2) The doctor has his/her line 4 as his / her private line
3) Nurses or clinical staff share their lines 2, 3 and 4
4) The receptionist / non-technical staff share their 3 lines 2,3,4
So in the above case regardless of how many phones you have, you have 1 line shared by all, the doctor has his/her own private line, and 3 lines each for the nurses/clinical staff and receptionist, for a total number of lines = 1 + 1 + 3 + 3 = 8 lines. Each station can transfer a call to any other phone in the office. A large number of physicians, dentists, and other providers use the system precisely as above (utilizing anywhere from 1 - 8 lines depending on your staffing/call volume), thus avoiding the considerable costs of a PBX or KSU phone system and professional installation.