Mr. Engineer

Your tech is technically correct. If you have more than the number of lines than the DKT2020 can display, any CO lines not shown, is difficult to access, esp if someone puts it on hold.

However, to overcome this, you can add a DADM to each phone but do look up in the General Decription on how many your DK280 can support.

Or, you can separate/group each CO line for each extension if possible.

I would not suggest a pooled-key solution either.

Wire Rat

You might want your tech to look at pooled line groups. On the receptionist phone you can have a DADM to account for all your lines so the recptionist will know what line is on hold.... Pooled line group keys for everyone else with a speed dial key of #5#70 (line pick up code) also on the key strip. You can have up to 4 pooled line group keys on one phone per line group. Enabling the employee to put a call on hold and use another line.
This way the recptionist tells the employee what line to pick up, they hit the line pick up key (#5#70), dial the 2 digit line position (ie. 01 for line 1) , and they are connected.

Just because you have 24 lines doesnt mean everyone will have to have 24+ keys to access them.

Chet