If you can use something, it's useful. Useful things are handy for whatever you're doing. If something is just what you need or you just find it helpful, then it's useful. A hammer is useful in building many things. Coasters are useful if you don't want a coffee table to get stains. College degrees are useful â or necessary â for many careers.
Where is the security key on a comcast modem located? The security key on a Comcast Modem is located next to the serial  number of the unit. Sometimes the serial number is the number used  as a security code if it is not printeâ¦d on the device. (MORE) 1 person found this useful.
If the modem connects to a router, unplug the Ethernet connector from the router and plug it in to your computer's Ethernet port. If the Comcast device combines a modem and router, it may have a single Ethernet port or multiple numbered ports. Connect to any of these ports.