tched analog and T1 trunks. Media gateways are responsible for managing some security, monitoring call qual- ity, detecting and transmitting off-hook conditions, and handling touch-tone, dial tone, busy signal, and ring-no-answer conditions. Media gateways transmit signals for VoIP such as ringing, call setup, and touch-tone in separate channels from voice calls. Analog Ports and Connections to the PSTN in Media Gateways Media gateways also contain ports for analog telephones. Analog telephones, which have similar electronics as older home telephones, are not compatible with IP networks. Data Centers and IP Private Branch Exchanges Analog ports are usually used for two functions: fax machines, and backup in the event of a failure. Some organizations have a backup analog phone for their central operator. If the LAN or the IP telephone systems fail, the organization will still be able to receive incoming calls. In IP telephone systems, the gateways are connected to the public tele- phone network and the DSPs perform the IP-to-circuit-switched conver- sions to make IP telephone system calls compatible with the PSTN. This conversion is not required for calls that bypass the public network and are transmitted over data networks. Connecting IP Telephones to Layer 2 Switches On IP-based systems, multifeatured IP telephones are connected to ports in Layer 2 switches on LANs. Computers and phones often share the same jack and cabling with the Layer 2 switch. In this configuration, the user's personal computer is plugged into a data outlet on the back of the telephone, and the telephone is plugged into the nearest RJ45 data jack. (IP telephones are often referred to as endpoints, a term for items such as PCs and printers connected to LANs.) RJ45 is the designation for a type of jack into which data devices plug to connect to networks. For greater redundancy and to create a dedicated path to the Layer 2 switch, the PC and telephone can each use a separate RJ45 jack, cabling, and port on the Layer 2 switch. This requires add