Hardware Technical Reference Manual
When the relays close, ONS 1 and ONS 2 on the AMB are automatically connected to the first
two LS trunk circuits. After power is restored and communication is re-established with the
controller, the relays open and the ONS and LS circuits function normally again.
When a system or network failure occurs, the controller checks for active calls on the ONS
lines and will only switch the ONS phones when they are free. When the network recovers, the
controller checks for loop current on the CO lines (active calls) and will only switch to normal
operating mode when no loop current is detected. This prevents the dropping of any ongoing
connection through the CO line during the recovery of the system.
To prevent dial pulses or hook flashes from triggering a switch to normal mode, loop current
breaks shorter than 560 ms are ignored.
You should plan carefully where you want the two ONS ports to terminate within the network.
If power is lost they will provide the only connectivity to the telephone network.
The two LS trunks do not have to be dedicated to support power fail transfer. You can place
them in a trunk group and use them to route calls to the central office during normal system
operation.
Music On Hold (AMB)
The MOH interface supports the following features:
• Transformer coupled input with DC blocking capacitor and 600 ohms AC input impedance.
• Limited signal level going onto the PCM stream.
• Fixed A to D gain.
Paging (AMB)
The Paging interface supports the following features:
• Transformer-coupled front end for audio signal with 600 ohms AC input impedance.
• DC load (as in an LS trunk) for 3
rd
party paging unit control.
• One FORM C relay for 3
rd
party paging unit control.
• Paging and answer-back audio path can operate in full duplex mode.
• Fixed A to D gain and D to A gain.
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