Model 3500-112

The Model 3500-112 is an economical ringing, tone and interrupter plant (50 to 100 watts).  It is designed to provide basic signals for residual ringing applications.



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


  • Size 10.5″ x 23″ (basic unit)
  • Up to 100 watts of ringing power
  • Short circuit protection
  • Self monitoring with automatic and manual transfer
  • Twenty distribution fuses included
  • Continuous ringing -AC/DC audible
  • Interrupted ringing at 2 seconds on 4 seconds off (code 1)
  • Grounds pulses interrupted at 10, 60 and 120 IPM
  • Space provided for any one redundant tone
  • LED indicators for system status
  • Alarm contacts for minor and major alarms
  • Remote reset of alarms
  • Many optional features


The Model 3500-112 residual ringing plant is designed to furnish ringing current and signals not supplied by the switch, yet needed for Private Line, Metallic Facility, Dial Long Line, Foreign Exchange, or Test Desk circuits. The many available options make the 3500-112 an economical choice for Residual Ring Plant applications.

The basic unit with redundant 50VA or optional 100VA ringing generators provides continuous and interrupted ringing current. Included are 20 GMT type distribution fuses (10 each continuous and 10 each interrupted). All fuses are mounted on a fuse panel with space available for expansion.

A supervisory system handles the monitor and transfer circuits and also generates 3 interrupted ground cadences. System status indicators and minor, major alarm contacts are also in the basic unit.

Optional features can easily be added to the basic unit either at the factory or later in the field. As an example, should a need arise for adding a tone, space has been provided so that plug-in circuit boards can be quickly installed. All options have been designed so a minimum amount of time and no special tools are required to install them.

Options and Ordering Information:

H – Basic unit with 100 watts of ringing
**A – Aux. alarm panel, provides additional alarm contacts
Z – Eliminates superimposed ringback tone (no extra cost)
I – Redundant 60 IPM ground pulse interrupter
R – Two additional relays for interrupting signals
*T – Redundant tone (specify Low, Ringback, Dial, or High)
**X – Isolation transformer for +/- 105v and + AC/DC circuits
E – Extended temperature range: -40C to + 65C
U – Agency approved versions
M – Ringing voltmeter and load demand monitor (model 4200)
MA – Alarm kit to extend load demand alarms
SK – Spare parts kit (varies depending on unit configuration)
HK – Upgrade kit to 100 watts of ringing (Field installed)
**FP – Aux. fuse panel for up to 60 additional fuses

*Tone option (includes 1 watt tone generators and 10 distribution fuses) should be ordered as follows:

T-L Precise Low Tone Option
T-R Precise Ringback Tone Option
T-D Precise Dial Tone Option
T-H Precise High Tone Option
Other tone options are available.

**These options add an additional 3.5″ to unit height.

Example Order

Ringing power 100W
Isolation transformer
Wide temperature
Low tone
Meter and alarm kit
Spare parts kit

Model 3500-112H/X/E/T-L/M/MA/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