Hardware Installation Manual  32  Document #: LTRT-28030 
5.3  Connecting FXS Interfaces 
The  device  interfaces with the FXS  analog telephone equipment  (e.g.,  fax machines, 
modems, or telephones) through the 50-pin Telco connectors provided on the FXS blades. 
For more information on the FXS blades, see Section  3.3.2 on page 21.  
 
 
Safety Notice 
•  Make sure that the FXS ports are connected to the appropriate, external devices; 
otherwise, damage to the device may occur. 
•  FXS ports are considered TNV-2. 
 
 
FXS Outdoor Cabling and Power Surge Protection 
•  The device includes an integrated secondary surge protection, but does not include 
primary telecom protection!  When the FXS telephone lines are routed outside the 
building, additional protection - usually a 350V three-electrode Gas Discharge Tube 
(GDT) as  described in ITU-T K.44 - must be provided at the entry point of the 
telecom wires into the building (usually on the main distribution frame / MDF), in 
conjunction with proper grounding. The center pin of the GDT (MDF grounding bar) 
must be connected to the equipotential grounding bus bar of the Telecommunication 
room.  
•  Failing to install primary surge protectors and failing to comply with the grounding 
instructions or any other installation instructions, may cause permanent damage to 
the device! 
•  The device complies with protection levels as required by EN 55024/EN 300386. 
Higher levels of surges may cause damage to the device. 
•  To protect against electrical shock and fire, use a minimum of 26-AWG wire size to 
connect the FXS ports. 
 
 
Note: To configure the current (mA) that the device supplies to the FXS ports in off-hook 
state, use the EnhancedFXSLineCurrent parameter. Configuration is applicable only to 
the first and last ports (e.g., 1 and 24) on each FXS connector. For more information, 
refer to the User's Manual.