first and foremost -- I want to say it can be done but it also cannot be done.
I do not condone using any of the downloadable VRS software for hearing people use just for calling thier deaf/hoh loved ones. I would LOVE to be able to distribute software, but then that is a whole another mess to discuss. To others that say try downloading it and try , it "can" work but if the VRS company finds out you are hearing using the software they will ask you to remove it and disable your account. FCC is very clear on this. They are only allowing free distribution to deaf/hoh under the stipulation that they would use it to call hearing people to "bridge the communication" gap as buying the software and service on top of high speed internet would be clearly a heavy financial burden.
Now having said this -- It really, really sucks not being able to have a way to call VRS software/hardware directly with ANYTHING else as a hearing person. There is nothing easily to purchase, or download that will work with VRS that is not tied to the VRS industry. diehardbiker is somewhat correct. the 1720 port is only hardcoded to the ring port to most popular vrs hardware and you know whom I am talking about. They use the noninteroperable video compression which makes things harder.
Second - you can do this on your own if you are a little computer savvy and you are running vista or older and you have a copy of netmeeting. you need to download netmeeting and install it on your pc as a XP program install properties. netmeeting is already including in XP but not supported anymore.
Now - Again -- what diehardbiker was trying to say, but I will say it here so the tags are there for a new search for people like you - You can only "get" video relay service by signing up with the current VRS service providers as long you are deaf/hoh and use asl. You just cannot use off the shelf products like skype, tango, aim, oovoo, camfrog, and many others with the deaf/hoh software/hardware combination. If anyone recalls - CSD put it out there in a query to the FCC to see if it "possible" to standardize the video industry as everyone wants to be able to communicate in any way and any form. Why cant we deaf be able to pick a certain hardware and software from our local store and EXPECT it to work with any VRS of our choice and STILL retain the current features we are enjoying? Imagine the possibilities of closing the communication gap?