If the telephone network offers simultaneous ring, a subscriber can set up any other numbers to also ring at the same time. These can be cell phone numbers or connections abroad. The number of parallel numbers which can be configured for each extension may vary between providers. Cell phone numbers and numbers abroad and other number rangers may also be limited. When using simultaneous ring on a network, a call will only take up one voice channel when answered.
Many conventional phone systems and modern cloud phone systems support simultaneous ring. Users are typically free to define if and how many internal extensions and external subscribers ring simultaneously when a call comes in. However, we should point out simultaneous ring on an external phone number will take up two voice channels on the phone system. The telephone first receives the incoming call and then forwards it to an external number via another channel.
The cost of simultaneous ring can vary greatly. Although simultaneous ring on internal extensions typically does not result in additional costs, forwarding it to an external extension or a cell phone can result in significant additional charges. After all, in this case the call charges from the actual extension to the number the call was forwarded to apply to both execution on the phone system and on the telephone network, and are charged to the subscriber who set up simultaneous ring.