Telesis PX24 IP PBX Business Phone System
Design and manufacture IP PBX Business Phone System, Switching System, VoIP Gateway, and Signaling Converter  

ISDN Signaling

Telesis Systems Offering ISDN Signaling

  • Telesis Business Phone Systems:
    • PX24M Hybrid IP PBX Business Phone System 
    • PX24X Hybrid IP PBX Business Phone System
  • Telesis Switching Systems:
    • X1 Large Capacity TDM - IP Telephony Switch
  • Combined VoIP Gateway and Signaling Converters:
    • Stillink 200
    • Stillink 800
    • Stillink 3200
  • Large Capacity IP PBX for Enterprises
    • Stillink 3200


Basic and primary rate ISDN interfaces are according to ETSI and ITU-T standards. QSIG ISDN D channel protocol is an ECMA (European Computer Manufacturers Association) derivative.

Types of Interfaces

For ISDN DSS1 Basic Rate (BRI) in PX24M, PX24X, and X1 systems, the types of interfaces supported are:

  • S0 interface
  • T0 interface
  • Uk0 interface

Both point-to-point and point-to-multipoint connection schemes are provided.

Basic Rate ISDN interfaces in Telesis systems

Telesis systems have Basic Rate ISDN interfaces to connect to NT and TE

For ISDN Primary Rate (PRI) in PX24X, X1 and Stillink systems, the types of interfaces supported are:

  • DSS1 Euro ISDN TE (terminal side)
  • DSS1 Euro ISDN NT (network side)
  • ECMA QSIG TE (terminal side)
  • ECMA QSIG NT (network side)

Primary Rate ISDN interfaces in Telesis systems

Telesis systems have Primary Rate ISDN interfaces to connect to PSTN and private network

Layers and Options

The physical layer of primary ISDN access in Telesis systems is an E1 (ITU-T G.703) interface. 120 ohm balanced terminations are supported on any E1. The line code is HDB3 or AMI programmable. CRC4 may be enabled or disabled.

Basic Rate ISDN interfaces are S0/T0 and Uk0. The connector type for S0/T0 is RJ45. Point-to-point and point-to-multipoint connection schemes are possible. With point-to-multipoint connections, both short and extended passive buses are supported. The line code on U interfaces is 2B1Q.

Several parameters in ISDN messages are programmable. Those are:

  • Calling-party number
  • Calling-party category
  • Calling-party type of number
  • Calling-party numbering plan
  • Calling-party presentation indicator
  • Calling-party screening indicator
  • Called-party number
  • Called-party numbering plan
  • Called-party type of number (fixed)
  • Called-party type of number (automatic by analyzing the called-party number)

ISDN Supplementary Services

The following ISDN supplementary services are supported:

  • 3PTY
  • AOC-D/E
  • CCBS
  • CCNR
  • CFU
  • CFNR
  • CLIP
  • CLIR
  • COLP
  • COLR
  • ECT
  • DDI
  • HOLD
  • MCID
  • MSN
  • UUS

Route and Routeset Configuration

In a Telesis system, each basic and/or primary ISDN access may have its own route number. It is possible to define up to 128 distinct routes. For primary access, a given route to a particular destination and its accompanying routes are grouped in a routeset. Each route in a routeset has a priority order. Routing to the next priority alternate route is possible in the event that a route becomes unavailable. Furthermore, it is possible to define which release causes stated in Layer-3 messages will lead to the alternate routes being used.

For accessing PRI, the channel selection type is programmable as ascending, descending, or cyclic. Disabling outgoing calls from certain channels also yields fractional E1 use.


A Telesis system may realize routing calls from ISDN interfaces according to:

  • Dialed digits
  • Calling-party number
  • Category of calling party
  • TON (Type of Number) of calling party
  • Numbering plan of calling party
  • Presentation status of calling party
  • Screening status of calling party

Related Readings

We recommend you to visit Telesis WiKi Pages for technical readings.


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