To confidently connect to the Internet via a telephone line, one modem is not enough. A splitter is just the device that will separate the signal from the server and another phone, providing the required Internet connection speed and no interference during the conversation.
When an ordinary telephone was being developed, it never occurred to anyone that telephone wires would one day be used to transmit a digital signal. Therefore, for the operation of the Internet and the telephone on the same line, a special separation device had to be used.
Why do you need a splitter
If a high-frequency signal (Internet, ADSL) works simultaneously with a low-frequency signal (PSTN), then noise in the form of noise will be constantly heard in the handset (the phone's electronics will “try” to decode the RF signal). On the other hand, the low-frequency component of the signal will "slow down" the transmission of information from the server, because the modem will count low frequency signals as an error that needs to be corrected.
To protect both signals (analog telephone and digital computer) from mutual influence, a filter (or splitter) is used, connected between the telephone cable, modem and telephone set. Externally, the crossover filter is a small plastic box with one input for a telephone cable and a pair of outputs for a device and a modem.
How does the splitter work
The filter divides the frequency band obtained at the input into 2 parts: one for the telephone signal, the other for the ADSL signal. As a result of splitting, the device outputs the corresponding frequency for each output jack. Telephone equipment, which includes devices, faxes, answering machines, etc., receives frequencies in the range up to 3400 Hz, and the modem - all frequencies over 25000 Hz.
If there are several telephones in the room on the same cable, then the splitter is installed at one outlet. In this case, you have to pull a separate wire to the modem from the ADSL output. This is not very convenient, since you will have to relocate (cross) the telephone line so that both the modem and the phones can work at the same time. The problem can be solved by using microfilters. These devices have one output, one input. A similar filter is installed in front of each telephone set. Sometimes, for convenience, manufacturers produce a telephone wire, which already has a built-in micro-filter in the form of a thickening. In some cases, the device is mounted directly in a junction box. The splitter is essentially an "advanced" microfilter. The latter works in exactly the same way as its “colleague”: it divides the frequency range without passing high-frequency signals into the phone; and prevents the penetration of low frequencies into the modem.
