US manufacturers of appliances using electromagnetic energy from 9 kHz to 300 GHz must seek equipment authorization from the Gummint. This is obtained from the Office of Engineering and Technology at the Federal Communications Commission.
The OET maintains an electronic database of all Certified equipment. The database can be accessed by the public through a web portal:
The best key for searching the database is the “FCC ID”. This identifier should be shown on the label of all equipment supplied to consumers within the USA.
(2Wire kit supplied via British Telecom to its end-users is usually absent an FCC label)
The FCC filings often contain information that can identify the mode of functioning of a device and the components within it.
The User Guide for the 2Wire 3801HGV is in the FCC filings, as is a block diagram of the 802.11 components in the 2Wires:
Documentation that 2Wire has filed with the FCC for its 802.11 devices is linked below, together with a local copy of the User Guide for the 3801HGV. 
If anyone has further links to 2Wire kit in the FCC database then please email and they will be added to the list, with attribution.
2Wire’s FCC filings for the 3801HGV
(Submission date: 01/28/2010 and 02/22/2011):
2Wire’s FCC filings for the 3800HGV-B and 3600HGV
(Submission date: 08/11/2008):
2Wire’s FCC filings for the 3700HGV-B
(Submission date: 10/25/2005):
2Wire’s FCC filings for the 2701HGV and 2701
(Submission date: 10/05/2006 and 05/02/2007):
2Wire’s FCC filings for the 2700RD and 2700
(Submission date: 07/15/2005 and 01/19/2006):
2Wire’s FCC filings for the 1801HG, 1800HG, 1701HG, 171HG, and 1700HG
(Submission date: 04/29/2005):