Frequently Asked Question
How to apply the FXO4-FXS4 converters and general questions answered?
Last Updated 5 years ago
There are two applications for these 2-wire analog POTS (Plain Old Telephone System) over fiber converters.
(1) Extension (all 4 channels)
+----------+ +----------+ +----------+ +----------+
| PSTN | | | | | | |
| or |======| FXO4 |----------o---------| FXS4 |======| telephone|
|analog PBX| | | | | | |
+----------+ +----------+ +----------+ +----------+
(2) Direct Hot Line (all four channels)
+----------+ +----------+ +----------+ +----------+
| | | | | | | |
| telephone|======| FXS4 |----------o---------| FXS4 |======| telephone|
| | | | | | | |
+----------+ +----------+ +----------+ +----------+
FXO (Foreign eXchange Office) device must always be placed with connection to the source of phone line (Public Switched Telephone Network, Private Branch eXchange, or Central Office) and MUST be 2-wire analog.
While the FXS (Foreign eXchange Station) device must always connect to 2-wire analog telephone or handset (POTS).
The DIP (Dual Inline Package) switches, on the cards, are only used to set the ring frequency for FXS or for the ring detection frequency for FXO.
In the extension application, the exchange will send a ring frequency to our FXO unit which in turn will tell the fiber connected remote FXS unit to ring the telephone. When remote telephone goes off-hook, normal phone communication will commence.
In the extension example, all 4 channels operate independently, but always from PSTN to telephone set. Channels are internally mapped 1:1; there is no provision for cross connecting channels.
In the Hot Line example, when a telephone goes off-hook, the remote phone will ring. Once answered, normal 2-way communication is established. These are private lines that run over fiber and are secure from EMI. Having fiber media, they are hard to tap, and by using proprietary optical encoding, nearly impossible to 'eavesdrop' on the communications.
The DIP switches are not involved in the on-hook, off-hook or analog signal for the voice communications, but instead are only for setting ring frequencies.
Ring frequencies are typically 20Hz for the USA and 25Hz for Europe. Just set the right code for your country. We have found that leaving all of these switches OFF will typically work everywhere.
In the extension application, the ring "cadence" follows the PSTN or PBX cadence. In USA, that is typically 2 second ring followed by 4 seconds of no ring and then repeating until the telephone is answered (code 1). Much of UK uses code 2 (1 second on, 1 second off, 1 second on then 3 seconds off), which we call the bloop-bloop ring. PBX may provide special cadences to indicate the call in originating from a local telephone extension or from an outside line. Our converters are transparent to cadence.
1. Please make sure the converters are positioned for either application 1 or application 2 above.
2. The 1-channel converters are configurable as either FXO or FXS by setting DIP switch. The 4-channel units are hardware fixed FXO or FXS and cannot be changed.
3. The 4-channel FXS units requires more power (8W) when actually driving the ring of a telephone. Do not use less than 12VDC for these units.
4. The 4-channel FXO units only requires 5W. Minimum DC voltage input should never fall below 9VDC.
5. The maximum allowed DC input before causing damage to these converters is 18VDC. Internal powered chassis for our cards supply 12VDC while for external adapter type chassis, we provide a 12VDC@1A (12w) AC to DC switching adapter (wall wart).
6. The single channel FRM220-FXO/FXS has been shown to be highly unreliable when used with fax or modem. In such cases, please use our 4-channel devices, FRM220-FXO4/FXS4 which work well with fax transmissions.
7. In the hotline/direct line application, we use a Code 1 cadence, 2 second ring followed by 4 seconds of silence.
8. If using vintage style telephones with mechanical (brass bells) ringing, please note: The single channel FXS model will only provide 70VAC ring voltage. The telephone will ring, but possibly not as loud as expected. However, the 4 channel FXS4 provides 90VAC ring voltage.
9. When off-hook, the FXS converters provide 48VDC to the phone line that simulates the voltage you would see on a PSTN.
10. These converters have no provision to work when two FXO units are paired (PBX to PBX).
(1) Extension (all 4 channels)
+----------+ +----------+ +----------+ +----------+
| PSTN | | | | | | |
| or |======| FXO4 |----------o---------| FXS4 |======| telephone|
|analog PBX| | | | | | |
+----------+ +----------+ +----------+ +----------+
(2) Direct Hot Line (all four channels)
+----------+ +----------+ +----------+ +----------+
| | | | | | | |
| telephone|======| FXS4 |----------o---------| FXS4 |======| telephone|
| | | | | | | |
+----------+ +----------+ +----------+ +----------+
FXO (Foreign eXchange Office) device must always be placed with connection to the source of phone line (Public Switched Telephone Network, Private Branch eXchange, or Central Office) and MUST be 2-wire analog.
While the FXS (Foreign eXchange Station) device must always connect to 2-wire analog telephone or handset (POTS).
The DIP (Dual Inline Package) switches, on the cards, are only used to set the ring frequency for FXS or for the ring detection frequency for FXO.
In the extension application, the exchange will send a ring frequency to our FXO unit which in turn will tell the fiber connected remote FXS unit to ring the telephone. When remote telephone goes off-hook, normal phone communication will commence.
In the extension example, all 4 channels operate independently, but always from PSTN to telephone set. Channels are internally mapped 1:1; there is no provision for cross connecting channels.
In the Hot Line example, when a telephone goes off-hook, the remote phone will ring. Once answered, normal 2-way communication is established. These are private lines that run over fiber and are secure from EMI. Having fiber media, they are hard to tap, and by using proprietary optical encoding, nearly impossible to 'eavesdrop' on the communications.
The DIP switches are not involved in the on-hook, off-hook or analog signal for the voice communications, but instead are only for setting ring frequencies.
Ring frequencies are typically 20Hz for the USA and 25Hz for Europe. Just set the right code for your country. We have found that leaving all of these switches OFF will typically work everywhere.
In the extension application, the ring "cadence" follows the PSTN or PBX cadence. In USA, that is typically 2 second ring followed by 4 seconds of no ring and then repeating until the telephone is answered (code 1). Much of UK uses code 2 (1 second on, 1 second off, 1 second on then 3 seconds off), which we call the bloop-bloop ring. PBX may provide special cadences to indicate the call in originating from a local telephone extension or from an outside line. Our converters are transparent to cadence.
1. Please make sure the converters are positioned for either application 1 or application 2 above.
2. The 1-channel converters are configurable as either FXO or FXS by setting DIP switch. The 4-channel units are hardware fixed FXO or FXS and cannot be changed.
3. The 4-channel FXS units requires more power (8W) when actually driving the ring of a telephone. Do not use less than 12VDC for these units.
4. The 4-channel FXO units only requires 5W. Minimum DC voltage input should never fall below 9VDC.
5. The maximum allowed DC input before causing damage to these converters is 18VDC. Internal powered chassis for our cards supply 12VDC while for external adapter type chassis, we provide a 12VDC@1A (12w) AC to DC switching adapter (wall wart).
6. The single channel FRM220-FXO/FXS has been shown to be highly unreliable when used with fax or modem. In such cases, please use our 4-channel devices, FRM220-FXO4/FXS4 which work well with fax transmissions.
7. In the hotline/direct line application, we use a Code 1 cadence, 2 second ring followed by 4 seconds of silence.
8. If using vintage style telephones with mechanical (brass bells) ringing, please note: The single channel FXS model will only provide 70VAC ring voltage. The telephone will ring, but possibly not as loud as expected. However, the 4 channel FXS4 provides 90VAC ring voltage.
9. When off-hook, the FXS converters provide 48VDC to the phone line that simulates the voltage you would see on a PSTN.
10. These converters have no provision to work when two FXO units are paired (PBX to PBX).