I just did a little searching, and it seems that the Italian R.A. = PBX in English.

The site listed below offers an explanation:
PBX Definition: Premise-based definition of PBX
The term PBX stands for Private Branch eXchange. A PBX, sometimes known as a phone switch or phone switching device, is a device that connects office telephones in a business with the public telephone network. The initial central functions of a PBX were to route incoming calls to the appropriate extension in an office, and to share phone lines between extensions. Over time, many functions have been added, such as automated greetings for callers using recorded messages, dialing menus, connections to voicemail, automatic call distribution (ACD), teleconferencing, and more.

Today, PBX systems are expected to handle a wide variety of duties beyond simple connection to the public phone system. The range of features offered by a PBX varies, usually in proportion with the price of the equipment. Some of the main functions:


Present a single business number that gives access to all company employees and departments
Answer calls with a custom business greeting
Offer a menu of options for directing the call, such as connecting to a specific extension or to a department
Provide a directory of employee extensions accessible by inputting digits corresponding to employee first or last names
Evenly distribute calls to a department among available employees through Automatic Call Distribution (ACD)
Place callers on hold when they are waiting for an available department employee
Play music or custom messages whenever callers are waiting on hold
Take voice messages for any employee extension, for a department, or for the company in general
Allow transfer of calls between extensions
Conference multiple incoming calls with employee extensions
Provide detailed call records and real-time system management

HTH
Catherine