LATA (Local Area Transport Area) - Telephone companies have divided some of their service areas into long distance calling areas called "LATA's". Your local phone company handles calls made within your LATA (Intra-Lata). The locations of your telephone is within a LATA. Your Phone Company uses this LATA for calculating you billing for calls made within your LATA and from one LATA to another LATA.

Latency -- The time delay for a signal (usually data) to propagate through a system. For instance, when accessing the Internet, when you enter a character into your PC, there is a measurable amount of time before that signal actually appears at the several points while traveling to its destination. Every element in that travel has its individual delay. Latency is that time delay.

Leased Line -- Usually refers to a twisted pair (phone line) that is Leased (rented), usually from your phone company, for exclusive 24/7 use from one location to another location. Leased lines do not carry voltages like dial-up lines, nor do they ring the telephone lines or go "off hook" (the line is connected 100% of the time). The highest speed data connections require a leased line of some type. Also known as "Dedicated Pair".  See also Nailed-up

LEC (Local Exchange Carrier) -- In the U.S., the "local phone company." If it used to be part of the Bell System (that is, owned by AT&T), then the LEC is owned by one of the seven RBOCs. Otherwise, the LEC is one of the hundreds of rural telephone companies that were never part of the Bell System and typically have under a few thousand subscribers each (though some have 500,000 or more). LECs own the central office(s) and the local loop (the cable from the C.O. to each of their subscribers) to provide communications services within a limited geographic area (called a LATA). After the AT&T divestiture, LECs were restricted from providing long-distance services (and the IXCs were restricted from providing local service), though this is changing. LECs can charge (that is, the call is a toll call) for longer-distance calls within their own territories.

Legacy Equipment - Any equipment that has come from predecessor or past equipment. Legacy equipment designs usually must maintain features and compatibility with the equipment of which it is replacing or complementing .

LSO (Local Switch Office) -- The central telephone office of which services your telephone.