Reference12r1:Interfaces/FXS/Advanced

The advanced settings of the analogue interfaces can be made here:

Optimization grade:	Present on ip22/24/28 gateways only As per default the TEL ports are optimized for low power consumption (Optimization 'high' and 'mid'). This decreases the usual on-hook supply voltage of 48V down to 24V. Most conventional phones and faxes can deal with this. In case a special phone is connected that cannot deal with this low voltage or if a long cable is used this dropdown can be modified. 'high' and 'mid' both set 24V on-hook voltage. The off-hook loop current is set to 20mA. 'low' sets 48V on-hook-voltage.
Ringing Voltage	present on ip22/24/28 gateways only This topic modifies the ringing voltage used for ringing. Ringing frequency is 25Hz. 'low' sets 65Vpk/45Vrms, 'mid' sets 68Vpk/48Vrms and 'high' sets 70Vpk/49,5Vrms AC.
Ring frequency	present on ip22/24/311/411 gateways only Ring frequency can be set to '25Hz' or '50Hz'. Normal ring frequency for all countries is 25Hz. The '50Hz' setting ins intended for test purposes.
Onhook voltage	present on ip311/411 gateways only Onhook-voltage can be set to '32V' or '48V'. Defaults to '48V'. Only used for test purposes.
Loop current	present on ip311/411 gateways only Offhook Loop current value can be set to values between '20mA' up to '40mA'. Note that higher values increases the power consumption of the gateway. The gateways are tested for all FXS ports running 30mA offhook-loop current. If some FXS ports are configured to a higher value, other ports must be configured to less than 30mA on order to NOT exceed the maximum available power of the POE switch. Depending on the switch behaviour, drawing too much power from the POE line may result in random reboots of the gateway as a result of a power shutdown of the POE switch. In this case, reduce the amount of FXS ports driving exessive offhook-currents above '30mA'.
Loop length	present on ip311/411 gateways only Loop length can be set to '500m' or '2500m'. Checking this topic to '2500m' decreases ring-trip threshold by 20% so that off-hook detection becomes more sensitive.
Loop length	present on ip28 gateways only Loop length can be set to 'low' for 500ft/155m or 'high' for 5000ft/1550m. Checking this topic to 'high' decreases ring-trip threshold by 20% so that off-hook detection becomes more sensitive.
RingTrip Threshold	present on ip22/24/302/305 gateways only Ring-Trip threshold can be adjusted using an absolute value in milliamperes.
Loop Current	Loop current can be adjusted using an absolute value in milliamperes.

Note: there is no difference between PoE and PSU powering of the IP2x.

For possible line lengths, see Maximum wire length.

Recommendation for Use with long Wire Length

For best performance with long wires, use the following settings:

• Optimization grade low
• Ringing Voltage 49.5 Vrms (high)
• Loop length 1550 m

The setting for Loop Current depends on the terminal requirements, not wire length.