Are netgear modems locked to a isp?

[ragne2]

ive got a netgear wireless cable voice gateway EMTA CVG824G v3, my friends father gave me this cause he wasn't using it, but i am not sure if i am able to use it cause i am on a AAPT plan and he is on a OPTUS plan, would it be locked to his ISP or not?

Please reply ASAP
Thanks you

Togie