I was looking up some info on Eircom’s wall-mounted DSL splitter boxes. Opening up the box, I found “UK Reg Des No 2097942”. This led me to the UK Patents website office, which turned up this design from Pressac Communications.

Browsing around Pressac’s website, I came across their Structured Cabling System Installation Manual which is a really useful reference. It covers everything from cable trays, testing, fibre splicing, intra-floor wiring, termination methods, and even fire-proofing.

I didn’t find the info I was looking for about the DSL splitters unfortunately, so I kept on looking. A friend is having problems with DSL line which I think are related to his Eircom Phonewatch alarm system. I wanted to understand how to connect the alarm system to his DSL splitter so that the analogue POTS signal loops through the alarm cabling while the DSL signal goes directly to the DSL socket.

After some more research, I’m fairly confident that it’s just a matter of disconnecting two resistors on the PCB and looping the alarm wiring through the IDC punchdown block labelled ‘alarm’. However, my searching did uncover another interesting page: DSL Nation’s Inside ADSL MicroFilters page, which has pictures of the internals of a large number of DSL splitters, along with commentary. Useful reading if you’re wondering why one DSL splitter is better than another.