ADSL Low Pass Filter

ADSL Low Pass Filter

What is a Low Pass Filter?

In electrical engineering, “break frequency” is that point in the frequency response of a system at which the flow of energy starts to decrease instead of passing through. Low-pass filters, as their name suggests, are electronic filters that regulate the amplitude of signals decreasing frequencies that are above the break frequency. They are an important and widely used tool in ADSL services.

Why are Low Pass Filters Needed?

Originally, telephone wires were designed to share “Speech between two destinations using a low band of frequencies (300Hz to 3400Hz). To ensure fast data traffic, ADSL uses a higher band of frequencies (25 kHz to 1.1 MHz). ADSL systems can be integrated into the same telephone line and can share the same wire at a time for data transfer because they both operate at different frequencies. However, the electronics hardware associated with a conventional telephone is usually not adaptive to high frequency signals of ADSL. This can lead to interference in the reception of the telephone line where high-frequency signals of ADSL can be recognized as resonating sounds and noise that cause annoyance and disturbance. This is where a low pass filter is used to separate two different components from the telephone line.

How do I Install a Low Pass Filter?

An ADSL Low Pass Filter is a small plastic box with a lead that goes into the telephone socket. It has one output each for the telephone and the ADSL Modem (some low pass filters have just a single telephone output). Once you are done connecting all the wires in their respective sockets, the ADSL filter chooses different bands of frequencies for the phone and the ADSL modem. It then sends the ideal band to the respective sockets. For optimum performance, it is essential that you separate all your telephony equipment with the ADSL filter. When installing an ADSL filter:

  • Make sure your phone and equipment is passing through a filter
  • Make sure that the ADSL signal passes through a single Filter

Make sure you use the same Filter for all phones