Functional Block Diagram - Blonder Tongue Laboratories Inc.

Broadband Specification Guide
Inserting a Local Origination Above a Cable TV Feed
Functionality
This system will allow you to augment the channel line up that is being provided by the local cable TV company,
and add channels made within the facility. This signal can now be handed off to a traditional coaxial distribution
network or a hybrid fiber/coaxial distribution network within the facility.
In Depth Description
This system is a variation on a system that was mentioned earlier; “Inserting a Local Origination In To
A Cable TV Feed”. This hybrid system replaces a channel on the existing cable TV line up with one that was
generated locally. The key to success in this system is correctly making space for the new channel above the
existing cable TV line-up. Once the band of channels to be eliminated has been identified, a low pass filter and
modulator must be specified.
The low pass filter makes room for the new channel by completely removing any signals above the unit’s
specified cross over point. The new channel is created by the modulator, which accepts audio and video
inputs and makes a cable TV channel. The low pass filter cross over point must be a lower frequency than the
modulator for the system to work. The low pass filter must be a very high quality filter so that it does not harm
the channels below the cross over point.
The keys to the success of this system are: a high quality low pass filter to completely remove the desired
band, and making sure that when the new channel is combined with the existing cable TV feed, it is done at
the correct levels so that neither signal damages the others. If you pick one product from each category on
the next page, you will have all of the components to ensure a working design. Once all of the products are
identified, the specifications can be looked up in the specification library at the end of this publication.
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