The advanced DSL modulation techniques usually use higher frequencies of bandwidth. Transmitting low-frequency legacy voice at the same time with high-frequency broadband information requires splitting the signals. In the residential environment, the traditional ADSL techniques use a splitter at the root of the internal wiring of the apartment. As the topology of the internal wiring is unknown, where it might be star, buss, or daisy-chained, the only place to install the splitter is in the root of this topology. This splitter eliminates the negative impacts of the internal wiring on the broadband signals, including reflections. However, by keeping the broadband signals far enough in the spectrum from the voice signals, the traditional splitter can be replaced with a micro low-pass filter in each of the telephone jacks in the apartment. This low-pass filter eliminates the high-frequency spikes that happen during the on-hook/off-hook transition of the handset. The penalty of moving the broadband signals far away from the voice is in the low achieved transmission bandwidth.

Installing a splitter in the user apartment requires additional wiring for sending the broadband signals to the customer premises equipment (CPE), which connects the user’s computing devices in one of the rooms in the apartment. A great advantage would be to create a splitterless environment, without the need for either splitters or filters. Splitterless installation avoids the need for a truck roll—i.e., sending a technician to the customer—which increases the installation cost by hundreds of dollars.

Figure 5 demonstrates a residential MDU system installation, where the link modules at the building’s wiring closet are attached, in a splitterless configuration, to the plain old telephone service (POTS) lines:

Figure 5. Building/MDU Splitterless "Add-On" Installation

Notice the wiring closet connection bridged onto the existing legacy voice lines without cutting them. The building blocks of the splitterless installation are included in the service switch (which will be explained later on) at the wiring closet and the CPE modem (see Figure 6).

Figure 6. The Building Blocks

The following diagram explains the CPE modem in-house installation. Because the CPE offers splitterless connectivity, the in-house wiring topology is transparent to the CPE modem installation and can be installed by the customer—just like a regular telephone.

Figure 7. In-House Splitterless Installation