The are several methods of getting POT's into Asterisk, see the main examples below:

• Port the POTs Number to an ITSP and use their services

  • Usually cheaper, especially if the internet service is not provided over the POTS line. Usually incoming calls are free and outgoing tariffs are cheaper than POTS. 

  • It involves little to no additional hardware and takes away a potential point of failure.

  • Failure of the internet connection will cause calls to stop working, but these risks are usually in the same ballpark as POTS.

• Use an analog adapter

  • This is usually cheaper than using a porting service, the devices are fairly simple to set up, and will also allow the use of an analog phone.

  • Great for failover if the Asterisk server breaks down, but poses itself as a point of failure.

  • A good example is: https://www.voipon.co.uk/grandstream-ht813-analog-telephone-adapter-p-8130.html

• Use an Asterisk card

  • PCI/PCIE Asterisk cards can allow POTS to connect directly to the server. Some manufacturers offer lifetime warranty, and they are usually scaleable.

  • These can get very expensive, especially if adding Hardware Echo Cancellation (HWEC - this is almost always required).

  • Being a server-hardware add-on, It may require knowledge of the setup - IE drivers, config files etc.

  • An example is: https://www.voipon.co.uk/sangoma-a200-fxo-fxs-analogue-card-pci-hw-echo-cancellation-a200-brmd-p-7279.html

• Use a gateway appliance

  • Usually for commercial use, a gateway is very similar to an analog adapter, but is built for enterprise.

  • Usually very expensive, but very robust.

  • An example: https://www.voipon.co.uk/sangoma-vega-50-europa-gateway-4-x-fxo-p-3804.html