What telephone set to choose?

Question

Telephony

Comrades, help is needed.
Need a bunch of phones director - secretary.
At the input we have a regular analog line with a city number.
On the secretary's telephone, you need the ability to receive calls and transfer to the director + call outside.
The director's office requires the possibility of internal communication with the secretary, the ability to make calls to the city, the ability to receive telephone calls transferred from the secretary.
How to establish such a connection? What do you advise?