If you have two separate phone lines the two lines wouldnt share the 9Mbps, they would share whatever was available to the batch of connections supplied to the addresses.
Its not possible to guarantee the second line will have the same speed but they wouldnt be sharing the same 9Mbps.
I think the guy above posted anyway, you can get a router that can take both ADSL lines and magic them together for you, thats the best way to do it, then someone can have the extra juice at any given time.
If you have 2 broadband connections each at 9Mb/s you could have 2 routers and 2 users connected to each router, but you can also get dual adsl routers that would connect to both broadbands giving you 18 Mb/s shared between all users which would likely make better use of bandwidth. Dual ADSL routers seem to start at around £300 but you might be able to get used ones at a lower cost.
Are you talking about just having two individual ADSL/FTTC Lines or are you talking about a Bonded Circuit like a Hatteras System?
If it’s just two individual lines technically yes they would both be around the 9Mbps range but depending on certain factors the 2nd line maybe more or maybe less than 9Mbps.
I remember years ago when I was a CST. This customer had two FTTC Lines, one he had when FTTC first became available on an ECI DSLAM and then years later got a second one, which was fed from a secondary Huawei DSLAM.
The line that was on the Huawei DSLAM obviously performed a lot better, by about 25Mbps if I remember right because it of course had Vectoring on it whereas the ECI didn’t.
I explained to him in great detail at least half a dozen times as to why but he couldn’t or just refused to get it and kept saying that because they come down the same cable from the PCP to his House surely they should be the same.
If you’re talking about a Bonded Line I’m not sure if BT/Openreach offer that Service for Residential Customers. They have or at least had the Hatteras System but that was for Business Lines and they paid a lot for it.
My broadband speed is 9mb/s
I want to double that.
Can I have a 2nd physical connection for a 2nd broadband?
Two different users would use each. Would each have 9mb/s or would they still share that speed?