A. FAQ on FXS gateways

1. Can extension lines in our FXS gateways with multiple lines call each other when it is configured as Single Server Mode?
In Single Server mode, all extension lines shares the same SIP number. Therefore, they cannot call each other. Config. By Line or Config. By Group mode should be used so that each extension line or each group has its own SIP number. In this case, calling between extension lines or groups can then be achieved.
2.   Can our FXS gateway work with all types of PSTN phones?
Not all PSTN phones work properly with our FXS gateways with the default telephone line interface settings. You may need to modify the following parameters via its built-in webpages.
a)          Telephone Line Voltage - Most PSTN phones nowadays works with telephone line voltage of 48 Volts. This parameter should be enabled as shown below.  If the line voltage is not configured properly, DTMF dialing may be affected as well.
b)          Ringing settings - Some PSTN phones may be designed to work with certain ringing frequency and pattern.   Modified these parameters shown below accordingly. Please note that the default ringing voltage is 48Volts sine wave without DC offset. Our old FXS hardware only support 48Volts square wave without DC offset. If your PSTN phone does not work because it requires higher ringing voltage or different ringing waveform, it is not compatible with our FXS gateway. Please use a different PSTN phone.  
c)          CID Settings - These parameter defines how CID / CLI signals are generated. Please note that only FSK based CID signals are supported. If your PSTN phone only support DTMF CID, it will not be able to display the CID of the caller. You will not to replace it with a PSTN phone that can support FSK CID signals if this CID feature is required.
CID FSK Mode defines whether the Bellcore or the ETSI FSK frequencies to be used. In the Bellcore standard, the Mark ("1") and Space ("0") frequencies are 1200 Hz and 2200 Hz. In the ETSI standard, they are 1300 Hz and 2100 Hz.
Not all CID call setup and timing parameters are support. Our FXS port only support CID signals with the call setup using 1st Ring. The duration of the first can be specified. In addition, the delay time between the end of the first ring and the generation of the CID signal can also be defined as Delay Time Before CID. The last parameter, Delay Time After CID, defines the silent period before normal ringing starts.
3. Does our FSX gateway support line reverse polarity?
Line reverse polarity is implemented on our FXS port when the called party answers a call. Some systems may require this line reversal as an indication to start counting the talk time for billing. 
4. Is FAX supported?
Only models HT-912T and HT-922T support T.38 and G.711 Fax mode.
5. Is VPN supported?
PPTP VPN with 40-bit encryption is supported. Please make sure your VPN server is configured for 40-bit encryption. 
The latest models HT-912T and HT-922T are already VPN supported. For earlier models, please upgrade firmware to version 31.5-15 via the link below. 
6. The RUN LED does not flash and the Line LED does not turn on when picking the PSTN phone connected.
The FXS gateway is damaged. Please return it for repairs.
7. No voice is heard when picking up the phone
Please make sure that the power adapter is properly connected to the FXS gateway. If the power is connected, the RUN LED should blinks. If not, the hardware is damaged. Please return it for repairs.
If the RUN LED blinks, the Line LED should light up. If not, please check to see if the phone is plugged to the correct phone jack. Please make sure that the PSTN phone is working. If the Line LED still does not light up, the hardware is likely damaged, please return it for repairs. 
8. What do you see from the LEDs and hear from the receiver of the phone when SIP registration fails?
If SIP registration fails, you will see that the RUN LED blinks at a fast rate and hears an abnormal tone (not a normal dial tone) from the phone receiver.