Model 3500-120

The Model 3500-120 is a redundant ringing current supply with output distribution fuses and load meter.



  • Residual ringing
  • Private Line
  • Dial Long Line
  • Foreign Exchange
  • Metallic Facility
  • Channel Bank
  • Special Services (911, Fire Bar, etc.)


  • Compact 3.5″ x 23″ size
  • Up to 100 watts of ringing power
  • Short circuit protection
  • Self monitoring with automatic and manual transfer
  • Ten distribution fuses included
  • real time display of ringing voltage and current
  • latch feature retains peak load
  • LED indicators for generator status and load demand
  • Alarm contacts for minor, major, fuse, and load alarms
  • Remote reset of alarms
  • Wide variety of voltages and frequencies
  • Many optional features


The model 3500-120 ring system is designed to supply ringing current to circuits not handled by the digital switch. These can be Private Line, Metallic Facility, Dial Long Line, Foreign Exchange, or Test Desk. The compact size and the many available configurations make the 3500-120 an excellent choice for Bulk Ringing applications such as Channel bank or Subscriber Loop Carrier circuits.

A standard unit will give the user a redundant ringing supply in 25, 50, or 100 watt choices and 10 distribution fuses. A meter is provided to monitor output voltage and current demand. This feature gives you the information you need on your ringing capacity as you plan for future growth. If loads exceed or get close to exceeding the capacity of your ringing supply you will be forewarned and save costly downtime and those hard to explain trouble tickets.

Options and Ordering Information:

L – Standard 25 watt system
M – Standard 50 watt system
H – Standard 100 watt system
A – Aux. alarm panel, provides additional alarm contacts
B – Superimposed audible ringback tone (no extra cost)
I – Redundant ringing interrupter module
F – Additional 10 distribution fuses in place of meter
X – Isolation transformer panel for +/- 105v circuits
E – Extended temperature range available: -40C to + 65C
U – Agency approved versions
SK – Spare parts kit (varies depending on unit configuration)
HK – Upgrade kit for M model to 100 watt (field installed)
FP – Aux. fuse panel for up to 60 additional fuses

Example Order


Ringing power 100w
Audible ringback superimposed
Interrupted ringing
Wide temperature
Spare parts kit

Model 3500-120H/B/I/E/SK

Download Manual: 

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Telecom Division Contacts:

Russ Arslanian, Sales/Marketing
Bill Murrin, Technical/Engineering
Dave Klingbeil, Technical/Engineering
Cora Rodgers, Administrative
Jenny Getchell, Administrative