Packet Switch is a router designed to read the destination address in an incoming cell or packet, consult a routing table and route the packet toward its destination. Packetizing is done in originating CPE and reassembly is done in terminating CPE. Multiple packet formats or protocols exist (e.g., x.25, x.75, frame relay, ATM, and IP).
Access Tandem Switch is a Switch used to connect End Office Switches to interexchange Carrier Switches. Qwest's Access Tandem Switches are also used to connect and switch traffic between and among Central Office Switches within the same LATA and may be used for the exchange of local traffic.
Tandem Switch or “Tandem Office” or “Tandem” is a switching entity that has billing and recording capabilities and is used to connect and switch trunk circuits between and among End Office Switches and between and among End Office Switches and carriers’ aggregation points, points of termination, or points of presence, and to provide Switched Exchange Access Services.
PBX means Private Branch Exchange.
End Office Switches (“EOs”) are switches from which end user Telephone Exchange Services are directly connected and offered.