Specifications

176 System Software Diagnostics Guide — September 2006
metallic circuit: A circuit in which metallic conductors are used and in which the ground or earth forms no part.
metallic loopback: Metallic loopback loops the data back to the network at the physical port on the back card of
a service module, whereas local loopback loops the data back to the network through the framer in the service
module.
OSD: Operating System Distribution.
payload: In a set of data, such as a data field, block, or stream, being processed or transported, the part that
represents user information and user overhead information, and may include user-requested additional information,
such as network management and accounting information.
payload loopback: A signal used to command the far-end receiver to loop back the received payload.
POST: Power-On Self Test. A series of diagnostic tests used to verify that the DM3 architecture board
components are working properly.
PSTN: Public Switched Telephone Network.
Public Switched Telephone Network: PSTN. A domestic telecommunications network usually accessed by
telephones, key telephone systems, private branch exchange trunks, and data arrangements.
signaling : To set up and tear down calls, some form of signaling is required (simple examples are ringing and
dial tone).
trunk: In a communications network, a single transmission channel between two points that are switching centers
or nodes, or both.
wink start: A signal sent between two telecommunications devices as part of a “handshake” protocol.