"I have an office at home and I would like to connect my phone and Fax machine to two of my Analog phones at the office. I have a cable modem at home and a T1 connection at the office. Would you please tell me first if this is possible and if yes what do I need to buy and what is the best brand to buy. I heard Grandstream is a good brand. Is that true?"
For your home you can use an analog adapter with 2 ports - 1 for fax & 1 for phone. I recommend the PAP2T.
You will need a voip service provider to give you a local telephone # if you wish to give this out for "non-voip" users to use with regular telephony equipment. We don't currently recommend a specific provider as there may be different alternatives that best suit your needs. The only required feature of a VoIP service provider is that you can "use your own hardware" - and that "they will help you provision said hardware".
For your Office with the T-1 - You can choose a Grandstream GXP-2000.
Yes Grandstream is a good brand and is cost effective.