Can I split my incoming coaxial cable that is connected to just one account into two (or more) branches with each having its end device (e.g. one TV, one modem or both modem)? I currently use it just for one end device (modem) but there is a 2 way splitter in a room where it enters the house so I was wondering if that can use the connection on its own. I have Comcast in Mid Atlantic USA.
In principal, yes you can do this. Practically, there are some design considerations that need to taken into consideration in order to get the best performance.
There is signal loss every time you split the cable. So first and foremost, the incoming signal strength needs to support the number of devices and splitters over the distance of the cable (longer cable = more signal loss).
When both cable modems and TV are used, often the signal is split closer to the source and a direct feed is provided to the cable modem. Some splitters have different loss levels for each connection and this is also used to provide higher signal strength for longer or runs or internet modems.
You should also contact your provider to ensure you can do this on your own.
Simple answer is YES you can use a tap to go to a tv but not another modem.
For tv what I would do is call Comcast, when the time comes, because what your signal strength is coming in to the house, will determine if Comcast will use a Tap or if they are going to need to install a in-line signal amplifier/Tap.
As for adding another computer just run cat5 or cat6 to the room and use a Giga switch if the modem does not have that capability.