FRM220-FXO / FXS 2-wire Fibre Converter

FRM220-FXO / FXS 2-wire Fibre Converter

The FRM220-FXO/FXS POTS phone line converter extender is used to connect PSTN voice signals to distant Plain Old Telephone (POTS) devices. FRM220-FXO/FXS provides a fibre media transport for POTS transmission and features an RJ-11C for copper connection. A pair of FRM220-FXO/FXS is required to implement an end to end system. FXO mode connects to a telephone line or PBX and has ability to detect ringing voltages and to act as a telephone. FXS mode is the reciprocal unit and has ability to act as PSTN and connects to a telephone device. When the FRM220-FXO/FXS card is placed in the FRM220 rack with SNMP management, in-band management allows viewing the card and remote converters status, type, version, fibre link status, on hook status and alarms. Both card and remote can be configured to enable or disable the port, reset the port and set the FXO or FXS mode.

The FRM220-FXS/FXO is available with either ST, SC FC/PC or a modular SFP based fibre port and both multi and singlemode optics are catered for. The copper telephony interface is presented as an RJ11 socket and the unit ships with an RJ11 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.

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

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

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-FXO/FXS 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-FXO/FXS 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 or modular SFP optics
  • 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: 1x9 (SC) or SFP LC
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)
  • RS232 RTS/CTS 5-wire
  • RS232 3-wire
  • Baud Rate: RS422, RS485 up to 1024kbps, RS232 up to 256kbps
  • Bit Error Rate: Less than 10-10

Indications: LED (Power, FX Link, Phone Act, 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)