Model 3500-115

The model 3500-115 is a full featured ringing,tone and interrupter plant (50 to 100 watts).  It is designed to provide all signals for residual ringing applications.



  • Residual Ringing
  • Private Line
  • Dial Long Line
  • Foreign Exchange
  • Metallic Facility
  • Channel bank
  • Test Desk
  • Customer Premise Supply
  • Exchange Ring Plant
  • Remote Terminal
  • Multi-Line Testing
  • Special Services (911, Fire Bar, etc.)
  • Apartment Door answering
  • Other Nonswitched Loads


  • Size 14″ x 23″ (basic unit)
  • Up to 100 watts of ringing power
  • Short circuit protection
  • Self monitoring with automatic and manual transfer
  • Fifty distribution fuses (30 ringing, 20 tones) included
  • Continuous ringing -AC/DC audible
  • Interrupted ringing at 2 seconds on 4 seconds off (code 1)
  • Redundant ground pulses interrupted at 10, 60, and 120 IPM
  • Redundant tone interrupter included
  • Space provide for up to 4 optional redundant tones
  • Space provided for single +48 vdc bias supply
  • LED indicators for system status
  • Alarm contacts for minor and major alarms
  • Remote reset of alarms
  • Many optional features


The model 3500-115 standard ring 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. This unit can also function as a primary source of ring, tone, and interrupter signals for a Central Office, Remote Terminal or customer Premise application. The many standard features and flexible options make this an excellent choice to meet present and future requirements for ringing and signaling.

A basic unit will give the user redundant ringing with 50VA or optional 100VA generators which provide continuous and interrupted ringing current. Fuses are included and pre-wired for all standard and optional outputs. This makes for easier field additions of plug-in options. A redundant interrupter with 3 interrupter ground cadences also comes standard with the basic unit.

Additional options can easily be added to the basic unit at the factory or later in the field. 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 3500-115H/X/E/T-L/M/MA/SK

Download Manual: 

Please fill out the following form to download the PDF 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