Globalstar Product Management – Technical Support

PBX Must Use “Loop Start” (not “Ground Start”) Interface for GSP-2900 and FAU200

leave a comment »

The Globalstar fixed phones, GSP-2900 and FAU200, provide a standard POTS (Plain Old Telephone Service) interface which can be used as an outgoing “TRUNK” line for a PBX.    There are two standardized signaling methods which are used by PBXs to manage a POTS trunk line — “Loop Start” and “Ground Start”.

  • Loop Start supervision is a supervisory signal from an end terminal to a switch in response to completing the loop path
  • Ground Start is a signaling method from a terminal to a switch where one side of a cable pair is temporarily grounded


Requirements for PBX Configuration and Compatibility:.

  • In order to use a Globalstar fixed phone as an analog trunk line on a PBX, the Globalstar tip/ring line must be connected to an analog FXO Loop Start voice port on the PBX.
  • This is because the Globalstar “fixed phone” products, GSP-2900 and FAU200, only support Loop Start.


Globalstar Fixed Phone Features to Support PBX:

Loop Start and Ground Start

  • The Globalstar GSP-2900 and FAU200 fixed phones detect Loop Start in accordance with BS 6305 and BS 6317.
  • Ground Start is not supported


Additional Features
The GSP-2900 and FAU200 fixed phones provide the following signaling methods to support the PBX:

  • Two-wire (tip/ring) Loop calling unguarded clearing protocol
  • Loop Current Break (clear backwards)
    • When a call is unsuccessful or cleared down by the far end, the fixed phone line interface delivers an appropriate tone (as determined by the network) followed by a break of the loop current.
  • Called Subscriber Answer (CSA) indication using Line Reversal
  • Immediate Ringing, used instead of ground start to reduce glare (call collision)
  • Call collision events are handled in a manner that gives priority to outgoing phone calls


Keywords:  Globalstar PBX compatibility GSP-2900 RAU GSP-2800 GSP-2400 FAU200 FAU-200

Written by Joseph Crowley

February 21, 2017 at 12:18 pm

Posted in FAU200, GSP-2900, PBX

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: