Plain old telephone service (POTS) splitters and microfilters are used
on telephone lines to ensure voice and data call quality. This document
describes splitters and microfilters and how and when to use them. POTS
splitters result in the best data and voice performance when the router and the
telephone are used on the same telephone line.
There are no specific requirements for this document.
This document is not restricted to specific software and hardware
For more information on document conventions, refer to the
Technical Tips Conventions.
This section explains the general purpose and design of POTS splitters
A POTS splitter (also called a splitter) is installed on a telephone
line that is connected to both data (high-frequency) and voice (low-frequency)
devices. The splitter routes the high-frequency and low-frequency signals on
the telephone line to the correct device. Signals intended for the router
disrupt voice calls. Signals intended for voice calls affect router operation.
Most splitters must be installed by the telephone company. However,
some are installed by the customer. If you are not sure what type of splitter
to use, contact your service provider.
This figure is an example of a type of POTS splitter that is installed
at the customer premises by the customer. Other types of splitters are
installed by the telephone company on an exterior wall of the customer
Microfilters are installed on telephones to improve voice call quality
when voice and data equipment use the same telephone line (twisted pair). You
should use microfilters when either of these two conditions exist:
The documentation for the telephone(s) you use with the router states
that microfilters should be used with the phone.
Poor telephone call quality is resolved by installing a microfilter
on the phone line.
This section describes the most common scenarios that use splitters
and microfilters listed from most common to least common.
This splitter, also referred to as a network interface device (NID), is
installed by the telephone company on the customer premises.
The router and telephone are on separate lines (twisted pair) to the
splitter. They share the same telephone line (twisted pair) to the Telco.
Microfilters are optional. They should be installed only if they improve
telephone call quality.
This splitter is installed by the customer on the customer premises.
The router and telephone share the same telephone line (twisted pair) to the
telco. Also, they are directly connected to the splitter. The splitter is
connected to the telephone line.
For additional telephones connected through the splitter, microfilters
are optional and should be installed only if they improve telephone call
For telephones connected directly to the telephone line, microfilters
Router and Telephone Using Separate Telephone Lines
The router and telephone are connected to separate telephone lines to
the Telco. The microfilter is optional. It should be installed only if it
improves telephone call quality.