User manual
 FIRMWARE VERSION 1.0.14.1   HT503 USER MANUAL  Page 25 of 64  
ROUTE CALLS TO PSTN 
The FXO port enables access to the PSTN network.  By default, the HT503 is in VoIP mode at off-hook. 
If “Route Call to PSTN” is configured, certain calls will be initiated from the FXO PSTN line port.  This call 
feature is especially useful for emergency calls or local telephone calls.  
To use this feature, users need to specify a special rule using the dial plan parameter located under FXS 
Port configuration page. If the dialed digits match the specified prefix, outbound calls will be initiated from 
the PSTN line. 
Note: The route to PSTN feature is only applicable to a  phone connected to the FXS Port. The 
configuration is done using the “dial plan” feature under the FXS tab.  An example of the configuration is 
{L: 911x+}. This shows that only calls that start with 911 are immediately forwarded to the PSTN line.  All 
other numbers will not be routed to the PSTN. An normal # would be: {L: 617x+|x+} or {x+| L: 617x+} 
For example, if “Route Call to PSTN” is configured as {L: 626x+}, all outgoing calls starting with 626 will 
be initiated from the PSTN line. 
FORWARD CALLS TO PSTN 
Any VOIP call may be forwarded to a specified PSTN number. FXO port should be registered with some 
preconfigured number (for example 1111). Any VoIP extension can dial this FXO account number and will 
be automatically forwarded to preconfigured PSTN extension. 
For example, if the end-user has configured a cell phone number in  the field “Forward to PSTN” under 
BASIC SETTINGS configuration page, all calls will be forwarded to the cell phone number after 4 rings.  
FORWARD CALLS TO VOIP 
By default, each incoming PSTN call is received over the FXS port.  The end-user may forward such a 
call to any preconfigured VoIP extension, in case the call is not answered in a certain number of rings. 
The  Default  value  of  the  parameter  “Number  of  Rings”  is  4.  This  parameter  located  under  “FXO  Port” 
configuration page. If during 4 rings, the incoming from the PSTN call is not answered, the call will be 
forwarded to another VoIP number previously configured in the field:”Forward to VoIP”.  This parameter 










