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Newsletter: Analog Terminal (FXO) and Network Port (FXS) Testing Using tProbe™ Client Server

Welcome to another April 2013 issue of GL Communications' Newsletter providing information and insight into our tProbe™ with FXO/FXS ports. The versatile tProbe™ can also support dual T1 E1 ports, dual datacom ports, dual VF In/Out ports, and an Ethernet port.


FXS and FXO are ports used by analog phone lines or phones. A Foreign Exchange Subscriber (FXS) port supplies ring voltage, battery current, dial tone and voice signals. Foreign Exchange Office (FXO) delivers an on-hook/off-hook indication (loop closure), DTMF digits, voice signals, and is usually a phone or fax machine.

The FXO and FXS ports on a tProbe™ simulate all of the above features. Also, the FXO port on the tProbe™ permits non-intrusive capture and analysis of voiceband signals from a two-wire telephone line.

Main Features

  • Script based simulation of 2-Wire Telephone Port (FXO) and Telephone Wall Jack (FXS).
  • GUI based testing of basic functionalities for FXO/FXS.

  • Standalone testing of FXO/FXS with loopback
  • Supports input and output signals of 8K samples/sec, u-law, A-law, and 16-bit Linear PCM
  • Functions supported by FXO port
    • ON hook and OFF hook (loop closure).
    • Transmit and Capture Traffic (digits, tones, and voice).
    • 2-Wire Calling/Answering, Caller ID, T1 E1 to 2-Wire FXO Drop or Insert, PC to 2-Wire FXO Drop or Insert
  • Functions supported by FXS port
    • Detection of "ON hook" and "OFF hook" status.
    • Ring and Battery Voltage Generation, Dial Tone Generation.
    • Transmit and Capture Traffic (digits, tones, and voice).
    • T1 E1 FXS Drop or Insert, PC to 2-Wire FXS Drop or Insert.
  • Loud speaker provided to hear the voice being transmitted on FXO/FXS ports.
  • FXO/FXS termination supports for over 70 different termination characteristics (different countries).


  • Testing gateways, VoIP ATAs, telephone lines, handsets
  • Voice quality testing, 2wire call automation, Caller ID
  • Monitoring signaling, voice, and tones on telephone lines non-intrusively
  • Generation and reception of traffic on 2-wire telephone lines
  • Remote operation of FXO FXS ports over TCP/IP

Typical Testing Scenario

tProbe™ FXO Port to Mobile or Landline Phone

The call flow shown here depicts the call from tProbe™ FXO port to the Landline or Mobile phone through the wall jack FXS, local PBX, and central office of the service provider and base station. With the tProbe™ FXO call script, one can perform the basic operations during the call setup such as the Off-hook/On-hook, check dial tone, transmit DTMF digits, monitor ring signal, and handling traffic.

tProbe™ FXS Port to a Regular 2-wire Phone 

The call flow shown here depicts the call from tProbe™ FXS port to regular phone (2-wire phone) via RJ-11 cable. Places the ring to regular phone (2-wire phone), captures the incoming traffic into the file and transmits traffic to the other end. With the tProbe™ FXS call script, one can perform the basic operations during the call setup such as monitoring Off-hook/On-hook, send dial tone, monitor DTMF digits, send ring signal and handling traffic.

For more information on the product feature, please refer to tProbe™ with FXO/FXS Ports web page.

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