After you have logged in over your SSL connection to the gateway, your browser will be told to open a new window for a heartbeat web page. Closing the heartbeat window will log you off, but you can move, resize, windowshade, hide or minimize it if you want to keep it out of your way.
The HTTP refresh header in that heartbeat web page tells your browser to automatically fetch a particular URL after a short wait. This regular heartbeat is how we make sure that you are not replaced by another user after you log in.
The number at the end of the heartbeat URL is a random key. It is given to your browser alone via the encrypted SSL channel. Each time your browser refreshes the page, it will be given a new random key, and asked to refresh again after a short wait. As long as your browser keeps refreshing each time with the proper random key, we know your heart is still beating, and you are still you.
If your browser skips a beat and requests the wrong key, you will be assumed to have been replaced by a new user, or by a previous user who has mistakenly reconnected using an improper IP address. The new user will need to log in as him- or herself before using the network.
Also, if your browser stops beating, after a minute you will be assumed to have either shut down, closed your heartbeat window, or moved out of range of the network. The next user of your IP address will then need to log in as him- or herself before using the network.
Finally, when you want to log off, you can do so instantly by clicking the "Log Off Now" link on the heartbeat web page.