Dry loop
（重定向自Alarm Circuit）
A dry loop is an unconditioned leased pair of telephone line from a telephone company. The pair does not provide dial tone or battery (continuous electric potential), as opposed to a wet pair, a line usually without dial tone but with battery.
A dry pair was originally used with a security system but more recently may also be used with digital subscriber line (DSL) service or an Ethernet extender to connect two locations, as opposed to a costlier means such as a Frame Relay. The pair in many cases goes through the local telephone exchange.