on-premises single line telephones (SLTs)

The system is compatible with 500 type (dial pulse) and 2500 type (DTMF) analog telephone devices.  This includes on-premises single line telephones (SLTs), fax machines, and modems. In DSX-40, SLTs connect to analog ports in the main equipment cabinet. In DSX-80/160, SLTs connect to SLIU PCBs. Each analog port provides power and ring voltage for the connected SLT.  The analog ports use DTMF receivers. Each system provides 10 DTMF receivers that are shared by all connected analog ports. Message Waiting Both DSX-40 and DSX-80/160 support FSK Message  Waiting lamps. DSX-80/160 also provides support for high voltage Message  Waiting lamps  – while DSX-40 does not. Ringing For Incoming Calls Single line extensions ring according to the settings in  2132-[01-64]: Line Ringing Stations: Config: Ring Line Ringing (2132): Ring Assignment] Assign: . It is not necessary to assign single line sets to Ring Groups to make them ring for incoming calls; they follow Key Ring instead. • In DSX-80/160 by default, the  first 16 extensions (300-315) ring (option 2) for lines 1-12 and  flash (option 1) for lines 13-64.  All other extensions have lamp only (no ringing) for all lines. • In DSX-40 by default, all extensions (including single line sets) have immediate ring for all lines. Ringer Equivalence Number (REN) Considerations DSX-40 Single line telephones assigned to Key Ring or the same Ring Group will ring simultaneously.  This is also true for single line telephones connected to the same port. Since the Ringer Equivalence Numbers of connected single line telephones are cumulative, you must do the following: • Add up the RENs of all connected single line telephones. • Be sure the total REN does not exceed 4 on any single port  or  system-wide. Note that a REN of 1 is normal for an industry standard 2500 set with electromechanical ringer. Many phones with electronic ringers have significantly lower RENs. Check the label on the bottom of each single line telephone for the REN value. DSX-80/160 Single line telephones assigned to Key Ring or the same Ring Group ring in pairs according to their SLIU PCB port assignment. For example, ports 1 and 2 ring together, followed by 3 and 4, 5 and 6, and  finally 7 and 8. If the system has more than one SLIU PCB installed, the respective port pairs ring simultaneously on each card (e.g., ports 1 and 2 ring simultaneously on each PCB).  The SLIU provides the capability to support this rin