Boxes without the analog passthrough feature only allow older, analog-only TVs to view digital TV.
If used with DTV converter boxes, these will need analog passthrough in order not to block incoming FM radio signals.
While this typically works to some extent with the converter box on, there is often significant signal strength reduction and/or interference on the original analog channels.
The majority of TVs have a button on the unit and/or remote labeled something like "TV/VIDEO", "INPUT" or "AUX", which manually switches between coax and other sources.
[2] In late March 2008, the CBA filed a lawsuit in the U.S. Court of Appeals for the District of Columbia, seeking an injunction to halt the sale and distribution of DTV converter boxes,[3] charging that their failure to include analog tuners or analog passthrough violates the All-Channel Receiver Act.
[4] CBA maintained that the lack of analog support would seriously harm the LPTV and class A television stations the group represents, as it is cost-prohibitive for many or most of them to convert to digital transmissions, and the new boxes would prevent viewers from being able to watch (or even being aware of the existence of) their analog-only stations.