Update status

Marc 2024

Here is a list of the main terms and areas of application that play a role at estos in connection with TSP. 



stands for TAPI Service Provider, also called TAPI driver.

PBX System TSP

System TSP

generally refers to the TSP of a telephone system
(provided by the respective manufacturer. The terms of use of the manufacturer apply, on which estos has no influence.)



is a middleware developed by estos especially for certain telecommunication systems.

ECSTA for SIP Phones

The solution consists of uaCSTA server for SIP phones and ECSTA for SIP phones.
They enable controlling and monitoring telephones from applications compatible with Microsoft TAPI.

uaCSTA Server for SIP phones 

  • uaCSTA Server for SIP Phones is a CSTA middleware for SIP telephones capable of uaCSTA.
  • provides controllable telephone resources to registered clients
  • functions by concept as a registrar and proxy
  • the central binding element between all participating components

ECSTA for SIP phones

  • As a telephony service provider (TSP), ECSTA for SIP Phones provides a TAPI conforming to standards.

Client TSP – Client TAPI driver

Client TSP

  • for outgoing dialing (send command, first-party) via the dialing help from the Microsoft Windows operating system
  • for outgoing dialing via Microsoft Outlook in Microsoft terminal server environments/Citrix XenApp environments
  • included in ProCall client for Windows

This functionality is available on SIP softphone lines.

Remote TSP – Remote TAPI driver

Remote TSP

For TAPI-capable third-party applications (network-capable, dedicated network connection) e.g. CRM/ERP application

TAPI line display, outgoing call (dialing help), or e.g. open window for incoming calls (application dependent, must be activatable in the third application)...

Monitor point inbound/outbound, signaling/line monitoring

directly accesses the TSP that controls the telephone system (system TSP or ECSTA)

not suitable for Microsoft terminal server environments/Citrix XenApp environments
(must be deactivated in ProCall client setup if necessary. Select "Do not install TAPI driver", use MultiLine TSP instead if necessary).

This functionality is not available on SIP softphone lines.

MultiLine TSP – MultiLine TAPI driver

MultiLine TSP

Provides any number of TAPI lines of the UCServer on another computer with Microsoft Windows operating system

Structure: Line display/line control between primary UCServer – PBX – MultiLine TSP – further (decentralized) UCServer

Tip: should usually be installed on the Microsoft Windows server of the primary UCServer.

Application areas:

  • TAPI-enabled third-party applications in Microsoft terminal server environments/Citrix XenApp environments
  • Cascading, location networking or centralization of telephony information
    Cascading with decentralized UCServers and MultiLine TSP is only necessary if the system TSP cannot be instantiated, i.e. if several telephone systems of the same type cannot be connected to one system.

This functionality is not available on SIP softphone lines.

Further information