The number of outbound calls that can be generated at once depends on the number of channel lines your business has. Only two third of the channel lines are used for making outbound calls and the remaining one third is reserved for receiving incoming calls. For example, if your business has 12 channel lines then, 8 channel lines are used for making outbound calls and 4 channel lines are reserved for receiving incoming calls. As 2 channel lines will be utilised to generate 1 outbound call, having 8 channel lines will generate 4 parallel calls.
You can utilise all your channel lines to make outbound calls.
Outbound calls cannot be made from channel lines that are reserved for receiving incoming calls.