How to organize telephone communication in the office between offices?

Question

Telephony

Hello, sorry for my stupidity.
I've been turning the Internet over and over for 3 days and I can't find it.
The task was set to organize telephone communication in the office, between the offices (departments) and the boss. So that the boss could immediately call and call someone to himself.
Can this be arranged?
That is, telephones are not needed with access to other city numbers, or mobile ones. But just inside the office.
Tell me where to start, how to implement what equipment I need, etc.
Thank you.

Answer 1

you need a PBX, IP phones (with PoE support if you do not want to be powered from power outlets) and infrastructure for them (cables, RJ-45 sockets, as well as either PoE switches or switches and power sockets).
start by choosing all this economy.
regarding PBX - you can take some branded one with SIP support (Panasonic, Avaya, etc.), you can take something a little cheaper (Yeastar), you can generally put a bare Asterisk on an existing server or a free virtual machine for free.
about phones - Yealink nothing devices IMHO. not the most expensive, not the cheapest and generally hassle-free. say SIP-T21 E2 or SIP-T21P E2. the boss and / or secretary can do something more interesting like SIP-T27G, to which you can then buy an additional block of buttons, if necessary.
well, and the implementation - stick it into your normally working network, set it up.

Answer 2

if you have at least one city number and (and) the Internet, many providers provide the "virtual PBX" service, i.e. they raise it (set it up) at home ... they assign internal numbers to your office phones and voila ... subscribers can call each other using these internal numbers ... this is how it is done in the remote office itself ..