The equipment needed depends on the complexity and use of the PBX — for example, the types of phones used at a particular site. In general:
telephone trunk (multiple phone) lines that terminate at the PBX;
computer with memory that manages the switching of the calls within the PBX and in and out of it;
network of lines within the PBX;
unified communications (UC) router — wireless and wired;
phone handset — Universal Serial Bus (USB), VoIP and Session Initiation Protocol (SIP);
cables, cabinets, uninterruptible power supply (UPS); and
telephony application server.
A PBX call center handles inbound and outbound calls and incorporates features to enable the automatic handling of inbound calls. These features include Interactive Voice Response (IVR); call monitoring to help assess employee productivity and provide training; conferencing capabilities; phone features that help agents answer and make calls from their desktops; integration to customer relationship management (CRM) systems that help capture logistics and bring up customer information to agents; and predictive dialer systems.
In some situations, alternatives to a PBX include a central office exchange (centrex) service in which a pool of lines are rented at the phone company’s central office, key telephone systems and, for small enterprises, primary rate Integrated Services Digital Network (ISDN).
PBXs installed within the enterprise are sold by numerous vendors. They include Nortel, Rolm/Siemens, NEC, Fujitsu, Cisco, Avaya and Alcatel-Lucent.