In the year 2000, many homes already had Optus Vision cable TV. When you added "Cable Internet," the technician would cut the existing lead-in cable and insert a splitter. One side went to your Set-Top Box (TV) and the other went to your Cable Modem. Because both devices needed to talk back to the exchange (the "return path"), the splitter had to be bi-directional (5 MHz to 1000 MHz).
HFC networks are designed with "headroom." The signal coming from the street tap was usually boosted high enough so that even after a 3.5 dB loss from a 2-way splitter, the signal reaching the modem is still well within the operating range.
It is a fascinating era to look back on! In 2000, that single coaxial cable was basically "magic," carrying hundreds of analog TV channels and "high-speed" 512kbps internet simultaneously.
The reason those installs worked so well without amplifiers was largely due to the 75-ohm architecture. Because every component (the cable, the splitter, and the modem) was perfectly matched to that resistance, the signal reflected very little. This allowed the technician to simply "tap" into the line and let the physics of the logarithmic decibel scale handle the rest.
If you ever stumble across one of those old splitters in a cupboard, you'll notice they are surprisingly heavy—that’s the high-grade shielding used to keep the "noise" of the early 2000s electrical environment out of your precious data stream.
Would you like to know more about how DOCSIS technology (the "brain" of the cable modem) has changed from those early Optus days to the current NBN speeds?