With iCap it is possible to perform an almost split-second switchover between captioners when necessary. The first captioner captions as normal. When it is almost time for the second captioner to begin, she (the second captioner) enters the provided access code. Then, they can set the timer on the middle-right of the iCap window to a small lead-in time to the amount of time that it will take the second captioner to begin listening and get ready to type; for example, try 15 seconds. After setting the timer to 15, press Start. The timer will begin counting down in seconds. When the timer reaches 0, the second captioner will replace the first captioner On-Air. So, the second captioner can begin writing while the timer is still counting down, and when the timer goes to zero, the live captioning will switch instantaneously from the first captioner's writing to the second captioner's.
However, in many situations, using the timer is not necessary. If the second captioner simply presses Start, with no timer, and then begins writing, her data will override the first captioner's data as soon as Start is pressed, and so the switchover delay should be a few seconds at most until she can switch from iCap to their writing software and begin captioning.
The first captioner will hear a tone from iCap, and will see that his Status window no longer says "On Air", once the second captioner has started writing.