Type-O carrier telephone

TYPE-O carrier, the most recent addition to the carrier series, is designed to supply additional telephone circuits to the many communities served by open-wire facilities. This new system supplements, rather than supersedes, the older open-wire systems such as types C, H, and J. Type-C and J carrier systems were designed primarily for long circuits, 2,000 miles or more, and consequently cost more than buying new wire for short distances. This leaves an important field of use for an economical short-haul carrier system, particularly below 150 miles.