#1 You can not have two DSL modems on the same phone number line.
#2 If you wanted to you could have two DSL modems, one for each phone number line.
For example for 000-000-0000 and for 000-000-0001.
Please note: Not vaild phone numbers, so don't even try to dail these.
#3 If I am not mistaken on Verizon Residential Service, you can't use two different modems with that account info in it.
#1 What problem/issue, are you trying to solve?
#2 What is the brand and model of your DSL modem?
#3 If you have more than one, like I do: Which one is connected to the phone line & power supply, and is turned on?