Globalstar Product Management – Technical Support

Globalstar Asynch Service — Recommended Landline Modems

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This article explains compatibility of landline asynch modems as it pertains to the ability of these modems to interface with the Globalstar Asynchronous data service.


  1. Recommended Modem:  The Globalstar modem is fully compatible with modems which use the Hayes chipset, for example Hayes Acura.
  2. Modems NOT recommended:  Modems which use either the Lucent or the Rockwell chipsets typically provide low performance, erratic connections.    There is a fairly low probability of establishing a reliable, successful asynch modem connection when interfacing to a non-recommended chipset.

Globalstar Gateway SoftModem Description:
The Globalstar IWF modem is actually a “soft modem” which is flash-loaded into the call processing card at the Gateway during call setup. Based on the format of the +MS command format for the Globalstar IWF, as described in the SDM Integrator’s Reference Manual, #80-99208-1, the modem type seems to be a “HSF” modem type. You can learn more about these modem types by using a search engine (such as google) with keywords “+MS”, modem, HSF, etc. There are several sites which explain the +MS command in more detail than the SDM manual.

Use Hayes Modems:
The Gateway modem seems to only negotiate successfully with Cisco Access Server 5300 or 5800 modems or with Hayes modems. They also connect with ZyXEL modems. The Gateway modems do NOT connect to Lucent modems.


Modems NOT to Use with Globalstar:

The Globalstar Gateway modem will NOT negotiate successfully with the following modems, all of which are made by Lucent (since Ascend is owned by Lucent):

  • Ascend TNT by Lucent
  • Lucent Port Master
  • Ascend Max 600
  • Nortel CVX systems also fail, and apparently use the Rockwell chipset


Failure Scenarios with Lucent and Rockwell chipsets:

  • If you use your Globalstar phone (or modem) to connect with modems that use an incompatible chipset, you may get a connection 1 out of 10 tries if you are lucky.
  • It is not worthwhile to spend any time trying to improve the success rate.
  • Many people have spent many hours modifying AT command initialization strings, and trying all sorts of other modifications of communications parameters, but to no avail.
  • This is not meant to indicate that the specified modems are bad; it is just that they are incompatible with the Globalstar system.



Other keywords:  asynchronous, async

Written by Joseph Crowley

June 15, 2017 at 9:13 pm

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