Chapter 7
DS0 VF Test Commands
Trunk types and seizure sequences
66
CT-650 Command-Line Reference Guide
Release 9.4
Trunk types and seizure sequences
Traffic on VF circuits starts with a seizure, which is an attempt to
request an individual circuit. When a telephone goes off-hook, it actu-
ally sends a seizure sequence to the central office, where special
equipment receives the seizure sequence and allocates a circuit as
required.
There are various protocols for seizure, depending on the type of
circuit. The standard sequence is delay dial, which is the sequence
used between a telephone and the central office that services the
phone.
Foreign exchange offices (FXO) use a different type of sequence. An
FXO provides service to a phone that is not in its normal service area.
For example, a company in the 212 area code (New York, NY) can
have an FXO in the 202 area code (Washington, DC). This enables
local calls between Washington and New York.
Another sequence is used for subscriber loop carriers (SLC). These
carriers provide service to more subscribers in a geographical area
than can actually be supported by the existing cable. Under SLC, more
than one subscriber can use the same VF channel.
For a complete list of seizure sequences for answering and dialing
calls on standard, FXO and SLC VF circuits, see
Description of VF test commands
The following sections describe the DS0 VF test commands.
Answer_Call
Transmits a series of answer call sequences over the channel selected
with the last
Monitor
command. The command enables switch-to-
switch or PBX-to-switch testing.
Syntax
Answer_Call <
> <
>
<
>
<
>
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