How come when the electricity is down telephones still work (even cell phones)

If it is a cordless phone it won’t work. Only the basic plug into the phone jack kind work. It all runs on low voltage, not amperage. That said, if in some places the phone wires are above ground and are cut I think it will also cut service.

The cell ‘phones and the direct link ‘phones do not use the same power source as the Electric Company. The ‘phone company uses its own supply lines.

@throssog so can you describe that power supply system for me?

@Ltryptophan Fairly simple I would think. The Non-portable ‘phone uses the line current that is in the ‘phone company supplied line. The cell’phone, of course, is battery operated and transmits through a tower that is independently supplied with power.

Telephones are working on DC voltage. The Phone Company buildings have huge generators and batteries in their basements to support the lines during power outages.
Additionally, Cell phone antenna sites and Phone Company remote sites have battery back-ups, which are required to be able to hold up service for 8 hours of electrical service interruption.

Telephone landlines are served by central offices that house the processing/switching equipment that provide “dial” tone, and route calls to their destinations.

These central offices are served by commercial power when that power is available.
When commercial power is lost, the central office has a backup battery supply that cuts in and assumes the power distribution to the processing and interoffice transportation equipment, and the recipient landlines.

Central offices also have their own power generators that usually take over for and eventually recharge the battery systems, once they’re online.

I know that some cell carriers, specifically Verizon Wireless, often have generators at cell sites and towers. So when power goes on, these generators go up and cell signal will not be lost.

For land lines, you can actually use the small power input to run a small lightbulb when the power’s out. I’ve never done that myself, so I have no idea how!

@CaptainHarley

Wow! I want to learn how to do that! haha

@CaptainHarley I discovered the painful way that if you are connecting those wires or doing anything that involves touching the bare conductor you will be knocked on your can if a call just happens to come in. Pretty brutal for low voltage.

Ditto to what most said above about only landlines that plug directly into a jack in the wall contiuing to work during power outage, portable phones won’t work. In addition to what has been said, many times part of city might have a power outage while others don’t. So, you might lose electricity on your block, but the phone company might have their power, so that is all functioning fine.

Question: if you have phone through your cable company and the electricity and cable go out, does your phone still work?

@woodcutter Yes, ringing voltage is around 90 volts a.c.—almost what comes out of electrical outlets & definitely in the lethal range.

@woodcutter

Yes, low voltage, but ( so I’m told ) high amperage.

… then again…

Ringing voltage is not in lethal range, but it stings bad when you cut a line that is ringing.
Over 100 volts, but low amps.

First of all, just because there’s a power outage at your house, doesn’t mean there’s one everywhere. Often times, a blown transformer can take out your house’s power, but leave on your neighbors nearby.

Second, the phone lines are a physically separate structure from the electricity service running to your power outlets. So neither is directly dependent on the other at your house.

Third, even if the primary plant and transmission lines that bring electricity to your house are completely offline, the phone company has access to more robust backups and can continue to provide the power for their phone lines.

Fourth, cell phones run on batteries and cell towers are on a different power grid than your home. Plus they have their own local power redundancy as described for the phone company in general.

Finally, as an aside, your cable television service will usually continue provide signal through your coax line during a localized electrical power outage, assuming you have a battery-powered television with which to watch it.