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TRUNKING TERMS AND CAPABILITIES C-11
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Main PBX
In a main—satellite/tributary communications network, it is the primary (main) node that handles all trunk
traffic for the connected satellite and tributary switches.
Main-Satellite Trunks
For the System 85, Generic 2, and DIMENSION PBX, this term refers to the 70 series of trunk types that are
used for connecting a MAIN switch to a Satellite or Tributary switch. The System 75 or Generic 1 will
typically use tie trunks for Main-Satellite applications. See the Trunking section of chapter 1 for trunk type
recommendations.
Off-hook
The station or trunk circuit condition for which the ‘‘loop is closed,’’ thus permitting dc current flow from
the distant end. Since dc current can flow, the distant end detects this and removes ringing current, if
present. See also E&M.
On-hook
The station or trunk circuit condition for which the ‘‘loop is open,’’ thus inhibiting dc current flow from the
distant end. See also E&M.
Out-of-Band Signaling
When a particular channel’s signaling information is transmitted in another channel, a separate time slot on
the digital facility.
Digit Sending Treatment
Refer to ‘‘Address Signaling,’’ ‘‘Senderized Mode of Operation,’’ and ‘‘Cut-Through Mode of Operation.’’
Party Test Signal
The primary use is with some early generation electro-mechanical COs. This signaling type exists on
DIMENSION PBXs and on System 85s through R2V4. However, there are no known current applications for
this type of signaling.
Precise Dial Tone
The dial tone signal returned by the terminating switch to the originating switch. This returned signal is the
second dial tone and serves to indicate that the terminating switch is ready to receive the addressing digits.
Precise dial tone is only applicable for certain trunk applications and switching systems.