Howto:Maximum wire length

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Applies To

This information applies to

  • IP21, IP22, IP24, IP28, IP29-x, IP302, IP311, IP411, IP2000, IP6000, IP3000, IP6010, IP3010, IP1060

More Information


The maximum wire length is determined by the wires resistance. It is limited to 2x30 Ohm.

Here is the maximum line length as a function of the cable's diameter

Cable diameter (mm) Maximium wire length (m)
0,4 200
0,6 450
0,8 800

Note that long cables running in parallel may cause interferences between the ports

analog FXS ports of IP22, IP24, IP28, IP29-x, IP302 TELx, IP311 TELx, IP411 TELx

These devices can operate 3 standards phones per port simultaneously. The maximum wire length (0.6mm diameter assumed) is 170m then. If there is only one phone connected per port, the maximum is 1700m. This is for talking. Ringing requires much higher voltage and depends heavily on the type of phone used. The maximum linelength thus can be less.

See also Recommendation for Use with long Wire Length in Reference12r1:Interfaces/FXS/Advanced.

What to do when analogue phones connected to an IP2x do not work correctly?

For green-IT efficiency, the IP22/24/28 will reduce the idle voltage from 48V to 24V. We have seen phones that do not work reliably with this reduced voltage (some of them do not ring at all, some ring too late and might miss CLIP information). If so, try to set the Optimization Grade in the Interfaces/TELx/Advanced settings to low.

Primary Rate (PRI) Interface of IP3000, IP6000, IP6010, IP3010, IP1060

The innovaphone gateways using chipsets for so called long haul method.

Maximum 300 meters is supported on ISDN Pri cable length, up to 600 meters are possible, from 600 to 1000 meters a third party adapter (for refreshing the Isdn signalling) can be necessary - never use over 1000 meter.

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