POS-point of service or point of sale. A terminal such as those used by gasoline service stations to charge customers for merchandise and services. A POS is a PC with an internal modem and software
Tandem switching allows the route of calls to a hub location prior to the reach of the final destination, where you can also modify the dial plan and destination pattern.
NTP uses the concept of a "stratum" to describe how many NTP "hops" away a machine is from an authoritative time source. A "stratum 1" time server typically has an authoritative time source (such as a radio or atomic clock, or a GPS time source) directly attached, a "stratum 2" time server receives its time via NTP from a "stratum 1" time server, and so on.
