Hello all,
I'm looking for help in choosing a suitable relay for a telephone switching project. I have an internet router with VoIP capability and so have my telephones plugged into that, not directly into the BT line. While the power is on, it works fine and with dialling rules or by prefixing the number I dial, I can make either a VoIP or PSTN call and the router switches it appropriately. However, during a power cut, all phones plugged into the router stop working. Unlike my old Draytek router, the new one does not fail-over to the PSTN when power is lost.
I would like to remedy this by making a switch box for the phones, so that when power does fail, all phones are automatically switched back to the BT line. There is no requirement to maintain a call in progress when the power fails.
My plan is to power a DPDT relay off the router's own wall wart (12V DC, 1.5A output), in series with the router, but what relay would be suitable? I've found a category of telecoms relays on the Digikey website, in which the following product appears:
Digi-Key - PB387-ND (Manufacturer - V23105A5303A201)
Would a relay like this be OK, or does the 'telecom' category refer to some other use? Any problems with powering the relay in the way I've described?
I believe the specs for a UK telehpone line are -48V line voltage, 40 mA current, 90V ring voltage.
many thanks,
R
I'm looking for help in choosing a suitable relay for a telephone switching project. I have an internet router with VoIP capability and so have my telephones plugged into that, not directly into the BT line. While the power is on, it works fine and with dialling rules or by prefixing the number I dial, I can make either a VoIP or PSTN call and the router switches it appropriately. However, during a power cut, all phones plugged into the router stop working. Unlike my old Draytek router, the new one does not fail-over to the PSTN when power is lost.
I would like to remedy this by making a switch box for the phones, so that when power does fail, all phones are automatically switched back to the BT line. There is no requirement to maintain a call in progress when the power fails.
My plan is to power a DPDT relay off the router's own wall wart (12V DC, 1.5A output), in series with the router, but what relay would be suitable? I've found a category of telecoms relays on the Digikey website, in which the following product appears:
Digi-Key - PB387-ND (Manufacturer - V23105A5303A201)
Would a relay like this be OK, or does the 'telecom' category refer to some other use? Any problems with powering the relay in the way I've described?
I believe the specs for a UK telehpone line are -48V line voltage, 40 mA current, 90V ring voltage.
many thanks,
R