Trapping uses a type of filter which is installed at the drop cable entering a subscriber's
home. These filters are usually place on a telephone pole or out of the reach to avoid fraud
by simple removal.
The filter is a completely passive device made up of inductors and capacitors, which attenuates the signal strength of
the premium channel so that the receiver does not get enough signal to provide an acceptable picture. This type of filter
is commonly referred to as a notch filter, which is sharply tuned and inserted before the customer's receiver. The trapping
filter will suppress the certain channel it has been designed to block and allow passage for all other channels in which
the subscriber has purchased. The frequency response of the trap can be arranged to cover a band of frequencies containing
certain channels, or blocks of channels, or all channels-in most cases this would be classed as no notch filter at all, but
one would be needed in the future if channel subscription changes are to be made.
This method is fairly weak in security since simple remove will open up the blocked channel(s)
Although this method is more secure than the 'jamming' method described later on this webpage.
To prevent tampering with the tuning so as to minimize the circuits rejection or unauthorized removal of the trap cable
companies often mount traps in secure environments such as sealed metal boxes or high up on the pole (not necessarily
secure since anyone with a long enough ladder can go up and have some fun :) )
This method is no longer favoured by cable companies since everytime a sunbscriber wishes to purchase a service a technician
would have to visit the premises and change the filter(s) accordingly, this becomes expensive for the the cable companies.
