LS Trunks
The analog boards interface with analog central office (CO) trunks on a -48 Vdc loop start (LS).
The LS trunk circuit has the following features:
• Ringing detection.
• On-hook signal reception for caller ID feature.
• Tip and ring voltage monitor.
• Software-controlled AC line impedance setting.
• Software-controlled audio gain settings in both transmit and receive path.
• Line reversal detection.
Power Fail Transfer (PFT)
The Power Fail Transfer (PFT) relays are activated by power loss (power fail transfer) or by
software directed transfer (system fail transfer). The following events will close the relays:
• Failure of the controller
• Interruption of the system AC power
• A controller reset.
DC Message Waiting Load Capability Not supported
DC Message Waiting Voltage No
Metering Generation No
On-hook Transmission Capability
2
500 ms, current feed < 1 mA
Positive Disconnect Yes
Ringing Frequency 20 Hz, 25 Hz or 50 Hz, balanced
Ringing Load Capability 2 REN (Ringing Equivalent Number)
Ringing Type balanced sinusiodal
Ringing Voltage (open cct) 55 V rms
Timed Flash Detection min. 100 ms
Notes
1. 5.17 miles (8.28 km) over 22-gauge cable with 300 ohm set, or 3.25 miles (5.19 km) over 24-gauge
cable with 300 ohm set, or 2 miles (3.2 km) over 26-gauge with 300 ohm set— minimum 40 Vrms
2. Used for sending CLID.
3. CLASS message only.
4. Supported on AMBv2 for CX only.
Table 16: ONS Station Line Circuits for the AMB (continued)
Attribute AMB (v1 to v3)
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