（单词翻译:单击）
OA&M
operation administration & maintenance
OCC
other common carriers
Ohms Restriction1
Ohms Restriction is the same as Ohms resistance. Ohms are measures of resistance. A resistance of one Ohm allows one Ampere2 of current to pass at the electric potential of one Volt3.
Open Systems Interconnection (OSI) standards
OSI standards are standards for the exchange of information among systems that are "open" to one another by virtue4 of incorporating ISO standards. The OSI reference model segments communications functions into seven layers. Each layer relies on the next lower layer to provide more primitive5 functions and, in turn, provides services to support the next higher layer.
Operating Telephone Company
An operating telephone company is any Bell-operating company or independent telephone company (termed exchange carrier in the MFJ) operating in North America.
Optical fibers7 are light guides for electromagnetic waves in the infrared8 and visible light spectrum9 composed of concentric cylinders10 made of dielectric materials with different indices of refraction (i.e., velocity11 of propagation normalized to the velocity of light in free space). At the center is a core comprising the glass or plastic strand12 or fiber in which a light wave travels. A low index of refraction clad surrounds the core and is itself enclosed in a light-absorbing jacket that prevents interference among multi-fiber cables. Multi-fiber cable can be purchased with between 2 and 136 fibers.
OPX
off-premises extension
OSC
operating system control
OSI
open systems interconnection
OSS
operations support systems or operational support system
Out Of Band Signaling
Out of band signaling uses the same channel path as the voice traffic but signaling is in a frequency band outside that used for the voice traffic. In digital systems, out-of-band signaling may take the appearance of an allocated13 bit position or a dedicated14 channel or time slot.
