PairGain PG-Flex FRC-754 L4, Manual

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Product Overview 363-754-104-01, Revision 01
4 June 22, 1998 PG-Flex FRC-754 List 4
Operational Capabilities
The FRC-754 List 4 channel unit provides eight loop start or ground start POTS interfaces between the RT and
subscribers, and performs the following functions:
• 64 kbps A-Law PCM encoding
• applies ringing voltage
• generates forward disconnect
• generates 12 kHz or 16 kHz meter tones
• detects an off-hook or ring-trip condition
• connects a subscriber loop to a metallic bypass pair
• protects against secondary surges
The subscriber line battery is supplied by a constant current supply. It is sufficient to operate a telephone set over
the indicated loop length. The battery feed can be disconnected and the loop opened to release subscriber
equipment when a forward disconnect signal is received from the FLC-704 List 4 COT line unit. The battery feed
polarity can also be reversed as a physical signal of far end supervision.
Circuit Operation
The following paragraphs define the FRC-754 List 4 circuit operation when using loop start for subscriber lines
or ground start for PBX lines. Each FRC-754 List 4 circuit has an associated LED that indicates when the line is
off-hook, idle, ringing, or under test (see
Table 1 on page 2 ).
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 Table 2 for circuit interactions).
Subscriber Initiated Outgoing Call. The following occurs when the calling line goes off-hook (see Table 2
on page 4 for circuit interactions):
• loop current flows and is detected by the FRC-754 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 FRC-754 List 4 COCU FRL-754 List 4 RTCU Subscriber
Circuit Idle No ringing
⇒
No ringing
⇒
⇐
On-hook
⇐
On-hook