Black box is just another tool used in phreaking that is also labeled as Agnew.
This is known as a miniature electronic device that is placed on a telephone which then allows a person to use it free of charge.
The advantage that this phreaking item offers is a bit limited, however.
The user will still be charged by the telecommunications company even if the user had a block box incorporated into his or her handset.
This happens mostly when the call comes from a telephone without a built-in black box.
Charged calls also occur when there are no processes installed in the telephone that may evade calls that are charged.
And was established in telephones during the years 1960s to 1980s. The main purpose of the phreaks for using such device is to offer the callers with telephone calls without the need to pay.
There are groups of people who abuse this kind of invention in which they place a black box into their telephones so that they can have longer conversations with each other.
They can have unlimited telephone calls without having the need to pay even just a single minute of all the calls they made.
Black box devices were also used for other purposes such as in the incoming modems of computers that operates the bulletin board systems.
The use of this phreaking tool became widespread way back during the years 1980s and the early part of 1990s.
This form of phreaking tool works in such a way that the feature of the telephone exchange is utilized.
In the telephone exchanges, the meter is activated only when the person on the other end of the line picks up the phone.
On the other hand, the meter is halted when the person being called at puts the telephone on-hook.
The black box is then used in order to deceive the meter, making an off-hook phone appear as if it remains on-hook.