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SCP-FRC754-042-03H
Subscriber Receives Incoming Call
The following occurs for an incoming call (see
•
FLC-704 detects a ringing signal from the CO
•
FLC-704 signals the FRC-754 which then connects ringing to the subscriber
•
subscriber line goes off-hook and the FRC-754, through the FLC-704, provides an off-hook condition to the
CO switch
Table 4.
Circuit Interactions When a Subscriber Receives an Incoming Call (Loop Start)
Operation
Subscriber
Idle
CO generates
ringing
Subscriber
goes off-hook
Ring trip
Busy Condition
The loop start busy condition at the RT is a Ring lead negative and a Tip lead positive with loop current flowing.
The same conditions occur at the CO (see
Table 5.
Operation
Circuit busy
Ground Start Operation
The following section summarizes the ground start sequences for on-hook (idle), subscriber inititated outgoing
calls, subscriber received incoming calls, and busy conditions.
Idle Condition
The ground start idle condition is a Tip-lead open and Ring-lead negative from the CO and Tip lead open and
Ring-lead negative at the RT (see
Table 6.
Operation
Circuit Idle
FRC-754 List 4B
Table 4
FLC-704
CO Switch
COCU
⇐
On-hook
⇒
Ringing
⇐
Off-hook
⇒
No ringing
Table 5
for circuit interactions).
Circuit Interactions for a Busy Condition (Loop Start)
CO Switch
FLC-704 COCU FRC-754 RTCU Subscriber
⇒
No ringing
⇐
Off-hook
Table 6
for circuit interactions).
Circuit Interactions for an Idle Condition (Ground Start)
CO Switch
FLC-704 COCU FRC-754 RTCU Subscriber
⇒
Tip - no ground
No ringing
January 6, 2003
for circuit interactions):
FRC-754 RTCU Subscriber
⇐
On-hook
⇒
Ringing
⇐
Off-hook
⇒
No ringing
⇒
No ringing
⇐
Off-hook
⇒
Tip - no ground
No ringing
Circuit Operation
5
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