Considering an upgrade/change from my TA624-5 to a TA-824. I noticed that CID for CO 1-3 comes standard along with 8 extensions. Installation manual clearly states that SLTs with caller ID display will display the CID info like they would on a POTS line with caller ID service which is a plus in my case.

My setup here is two buildings, office/shop for home business and house 15 ft away and Cat5e cables for phone and network run between underground in conduit. The PBX controller is in the business building and in the business I will be using display PT phones but I have a fax machine capable of showing the incoming number via CID service. I need to have 2 ports for a TVS50 as an answering machine like I do with the TA624 which leaves 6 EXT ports if the basic 3x8 config. The business building needs phones in a woodshop, assembly shop, bench area and 2 desks in the office. Just me and the wife, she mostly does her thing in the house. CO 1 will be our business incoming line, CO2 will be for outgoing and for a calldesk line when I start working with that kind of work later. House does not need to access CO2.

Ok here goes. Can I get away with an 8EXT setup - if I use one extension assigned to just CO1 and run it to the house and parallel 3 SLTs on that line? Could I put more than one display PT on an extension in the business building - say my woodshop and assembly shop on the same extension cable with 2 PTs paralleled? Would that work and them both ring at the same time and both auto-answer in intercom mode? Or do I really need the second card to give me 16 extensions to do what I want for both buildings?

Finally the TA824 doorphone card looks an awful lot like the TA624 doorphone cardthough they are different part numbers. I suppose the TA624 doorphone card would NOT work in a TA824. If it will I'd like to know. I know my TA30865 doorphones will work with either model Ta624 or TA824 and that my T77xx phones will work with either system and that the current 2 pair for PT and 1 pair for SLT will work on either.

Greatly appreciate any insight on this to help with deciding on this.