Internal lines vs external lines --- noobie question

Lets say I have one single analog line coming in. It plugs into my sipura 3000, then goes to my asterisk box via a gigabit switch. If I’m on the phone (line 1), other people in my office can still hit another “line” (ex. line 2) and get a dialtone and dial an extensions within our network, right?

…or is it the case that if the incoming external line is used, then no one can dial anyone else’s extension until I’m off the phone?

I guess my question is — is there a difference between external lines (that connect you to the outside world) and internal lines (that connect you to other extensions and voicemail, etc…) ?

If it matters, we’re using Grandstream GXP-2000 phones.

I did try looking first (google - asterisk internal external lines) and had no luck.

The device has only one fxo port to connect to the pstn, so only one internal to external or external to internal call is possible at given time.

Cheers.

Marco Bruni

Strictly inside the network, when personA is on a call with an external number (the single external line is in use), can personB pick up their phone, hit “line 2”, get a dial tone, and dial personC’s extension?

*personA, personB, and personC are all inside the network

Another way of asking it: With an external to internal call taking place (the single external line is in use), can an internal to internal call take place?

Yes, I think this should be possible but I don’t own and never test this device so can’t be 100% sure.

Cheers.

Marco Bruni

After research, and real hands-on experience, here is the answer to my questions:

Yes, there is a big difference. Regardless of how many external lines you have connected (or, in use) to the PBX, you can still have internal to internal calls as long as you have an available “line” on your phone (hardware).