Product Overview
363-704-104-01, Revision 01
4
June 22, 1998
FLC-704 List 4
Operational Capabilities
The FLC-704 List 4 channel unit provides eight loop start or ground start POTS interfaces to the CO switch. The
unit performs the interface function between the analog POTS circuit and the internal digital pulse coded
modulation (PCM) bus. In addition, each channel unit:
•
detects forward battery
•
detects ringing voltage
•
detects reverse battery
•
detects Tip ground and Tip open
•
detects 12 kHz or 16 kHz meter tone
•
detects a subscriber test access signal
•
provides loop closure
•
provides grounded ring lead
•
converts analog signals to and from 64 kbps A-Law PCM digital format
Circuit Operation
The following paragraphs define the FLC-704 circuit operation when using loop start for subscriber lines or
ground start for PBX lines. Each FLC-704 circuit has an associated LED that indicates when the line is off-hook,
on-hook (idle), ringing, or under test (see
for front panel LED definitions).
Loop Start Operation
The following section summarizes the loop start sequences for on-hook (idle), subscriber inititated outgoing calls,
subscriber received incoming calls, and busy conditions.
On-hook (Idle) Condition.
Loop start idle condition is a Ring-lead negative and Tip-lead positive from the CO
with the same condition out of the RT toward the subscriber (see
for circuit interactions).
Subscriber Initiated Outgoing Call.
The following occurs when the calling line goes off-hook (see
for circuit interactions):
•
loop current flows and is detected by the FLC-704 List 4 channel unit
•
FLC-704 receives an off-hook signal from the RT
•
FLC-704 generates an off-hook condition to the CO switch
•
CO sends dial tone
•
FRC-754 passes a dial pulse or Dual Tone Multi Frequency (DTMF) signal through the FLC-704 from the
subscriber and forwards these to the CO
Table 2.
Circuit Interactions for an Idle Condition (Loop Start)
Operation
CO Switch
FLC-704 List 4 COCU
FRL-754 List 4 RTCU
Subscriber
Circuit Idle
No ringing
⇒
No ringing
⇒
⇐
On-hook
⇐
On-hook
