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Data Sheet

User Manual

Analog Loud Ringer & Paging Amplifier

The Algo 1825PM Duet Plus is a high-performance low-frequency loud ringer for high noise / wide-area environments where telephone ringing is difficult to hear (e.g. factory, machine shop, warehouse, lunchroom). The Duet Plus can also help to avoid missed calls due to hearing impairment. The device interfaces to a CO line or with any telephone system via an analogue FXS port, ATA or contact closure such as a night bell.

Loud ringing can be activated by a relay or switch closure (dry contacts), low voltage detection, 90V analogue telephone ringing, or the headset jack on selected Nortel Norstar and BCM digital business telephones.

Non-Irritating Tone Output

The 1825PM Duet Plus can be wall mounted in office or quiet warehouse applications utilizing its built-in speaker to generate up to 93 dBA (at 1m) warble tones. An optional 1186 Horn Speaker is available for very loud or outdoor requirements (112 dBA at 1m). The combination of lower frequency warble and high sound pressure levels create an extremely effective and pleasant telephone alert for large or noisy locations.

Amplified Voice Paging

An additional feature of the 1825PM Duet Plus is its capability to provide amplified voice paging as a separate application or in combination with loud ringing utilizing the same speaker. For small business applications, this provides an extremely cost-effective solution for loud ringing and paging into a warehouse, storage yard, or machine shop. Separate volume control is provided for the voice page and loud ring levels.

Other useful features include adjustable warble frequency, adjustable volume, and integrated test button.

Key Features

  • Convenient 90-volt ring detection via an RJ11 modular jack
  • Avaya IPO connectivity directly to an FXS port for “wet” paging
  • Auxiliary speaker outputs for connection to existing paging systems
  • Dry contact activation from push-button, Algo door phone controllers, or PBX Night Bell/Auxiliary Ring contacts
  • Operational from the headset jack of Nortel Norstar and selected Meridian 1 station sets
  • Easy connectivity to BCM Media Services Card using optional 2503 BCM Connector Kit
  • Visual Ring indication with optional 1128 Analog LED Strobe Light or 1127 Visual Alerter
  • Low-frequency tone output provides effective non-irritating notification of telephone and paging signals
  • Interfaces easily with optional Algo 1186 Horn Speaker to provide increased ringing or voice notification volume (up to 112 dBA SPL at 1m (3.3ft.))
  • Adjustable volume and frequency controls to suit user preferences
  • Designed for easy wall mounting


  • Machine shops
  • Warehouses
  • Outdoor work yards
  • Factories
  • Farms
  • Lunch rooms


Item Description
High-performance low-frequency loud phone ringer compatible with dry contact closure events, analogue telephones, and Nortel Digital Telephones including Norstar, BCM, Meridian 1, and CS 1000.
Power supply Adapter included;
22V 350 mA Class II
Maximum wire distance 500 feet (150m) for remote power using 24 gauge wire
Sound pressure level 93 dBA, 500 Hz 3.3 ft (1m) using internal speaker; 112 dBA, 500 Hz 3.3 ft (1m) typical with 1185 Horn speaker
Warble frequency Adjustable 290/360 Hz to 770/960 Hz typical, 4 to 12 Hz modulation
Output power
(for external speaker)
6 W peak, 3.5 Wrms continuous into 8 Ohms
Output impedance (for external speaker) 8 Ohm in power mode, 10kOhm in line driver mode
Dry contact closure Detection with 10Vdc 1 mA
resistive circuit
90V ring detection REN 0.2, ring start 40Vrms; ring stop 27Vrms
Low voltage detection Detects external 3 to 60V dc or ac
Paging input 600 Ohm balanced and isolated
Paging input level Selectable, 0 dBm (HI) or
–18 dBm (LO)
Audio detection -43 to +12 dBm adjustable
Dimensions 5-3/8″(H) x 3-1/8″(W) x 1-5/8″( D); 137 x 79 x 41mm