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Fibre Optic Telephone Extender

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FRM220-FXS/FXO - Telephone over Fibre

FRM220-FXO / FXS 2-wire Fibre Converter

The FRM220-FXS/FXO Fibre Optic Modem allows the extension of a single analog telephony service over fibre cabling. The unit can be employed as a fibre optic telephone extender but can also be used to connect to any analog device that uses the 'voiceband' such as fax machines. analog dial-up modems and EPOS terminals.

FRM220-FXO / FXS 2-wire Fibre Converter schematic 1

FRM220-FXO / FXS 2-wire Fibre Converter schematic 2

The FRM220-FXS/FXO is available with either ST, SC or a FC/PC fibre interface and both multi and singlemode optics are catered for. The copper telephony interface is presented as an RJ-11 socket and the unit ships with an RJ-11 to BT adapter cable for direct connection to UK terminal equipment.

Configuration is simple, using a single DIP switch select either FXS (subscriber) or FXO (exchange), connect the cables and they're up and running. Alternatively the unit can be located in a chassis with an NMC management card and all configuration can be achieved remotely via HTTP or SNMP.

The NMC card also allows the remote FRM220-FXS/FXO unit to be configured by means of an embedded communications channel contained within the fibre. Additionally the NMC card enables the status of the link to be monitored, one can view the health of fibre link and if the telephone is 'off hook'. Should an alarm condition occur (eg the fibre is broken) a 'trap' is generated and sent to the management station.

The FRM220-FXS/FXO can also be used in 'hotline' mode. 2 units are used, both configured as FXS and a telephone connected to each. As soon as 1 telephone goes 'off hook' the other rings. The FRM220-FXS/FXO also has the capability to pass caller-id information.


  • Fibre optic telephone extender - up to 120Km over singlemode fibre
  • Support for any voiceband analog device - dial-up modem, etc.
  • Fixed fibre port - ST, SC or FC/PC
  • Simple configuration via DIP switch - FXS / FXO
  • Can be managed and monitored via NMC management card
  • Supports transparent passing of caller-id information
  • Support for 'hot line' mode


Optical Interface:

  • Connector: ST, SC or FC/PC
  • Fibre: MM 62.2/125μm, 50/125μm. SM 9/125μm
  • Distance: MM 2km, SM 15/30/50/80/120km; WDM 20/40/60/80km
  • Wavelength: MM 1310nm, SM 1310, 1550nm, WDM 1310Tx/1550Rx(type A); 1550Tx/1310Rx(type B)

Electrical Interface:

Connector: RJ-11
FXO Mode:

  • Impedance: 600 ohms
  • Coding: 16 bits liner
  • Loop Current: 10~100mA
  • Ring Frequency: Acceptable 20 ~50Hz
  • Insertion Loss: 0.0 ± 1.0dB at 1000Hz

FXS Mode:

  • Impedance: 600 ohms
  • Coding: 16 bits liner
  • Dial: DTMF and Dial Pulse
  • Battery Source: 48VDC ± 4V
  • Ringing Waveform: Sine wave
  • Ringing Frequency: 20/25/30/50 Hz selectable
  • Ring Cadence:
    • FXS to FXS: On / 1 sec, Off / 2 sec
    • FXO to FXS: Reproduces the cadence detected by FXO
  • Insertion Loss 0.0 ± 1.0dB at 1000Hz
  • REN: 4.0B(Ring Equivalence Number)
  • Bit Error Rate: Less than 1010

LED's: Power, Fibre Link, Phone Off-Hook, Test
Power Input: Card : 12VDC, Standalone : AC, DC options
Power Consumption: < 5W
Dimension: 155 x 88 x 23mm (D x W x H)
Weight: 120g
Temperature: 0 ~ 50°C (Operating), -10 ~ 70°C (Storage)
Humidity: 10 ~ 90% non-condensing
Certification: CE, FCC, LVD, RoHS
MTBF: 65,000 hrs (25°C)