The U.S. Robotics brochures for the USR-310, USR-320 and 
USR-330 modems were published without a copyright notice. 
The exact publication date is not known but it is before 
March 1978. Any work published before January 1978 without 
a copyright notice is in the public domain. Works published 
in 1978 through March 1989 without a copyright notice could 
be registered within 5 years. If no registration was made 
the works are in the public domain.

A search of the U.S. Copyright Office records can be made here:
http://www.copyright.gov/records/

A search for U.S. Robotics returns 15 items. The schematics 
for these modems were published on January 3, 1978 and 
registered in July 1978. There are no entries for the 
brochures or any other works in 1978. These brochures 
are in the public domain.


========================================================

Type of Work:      Visual Material

Registration Number / Date:
                   VA0000005434 / 1978-07-13 

Title:             USR-310 originate acoustic coupler.

Description:       Schematic diagram.

Copyright Claimant:
                   U. S. Robotics, Inc.

Date of Creation:  1978

Date of Publication:
                   1978-01-03 

Names:             U.S. Robotics, Inc.

========================================================

Type of Work:      Visual Material

Registration Number / Date:
                   VA0000005431 / 1978-07-13 

Title:             USR-320 auto-answer modem CBS.

Description:       Schematic diagram.

Copyright Claimant:
                   U. S. Robotics, Inc.

Date of Creation:  1978

Date of Publication:
                   1978-01-03 

Names:             U.S. Robotics, Inc.

========================================================

Type of Work:      Visual Material

Registration Number / Date:
                   VA0000005430 / 1978-07-13 

Title:             USR-320 auto-answer modem CBT.

Description:       Schematic diagram.

Copyright Claimant:
                   U. S. Robotics, Inc.

Date of Creation:  1978

Date of Publication:
                   1978-01-03 

Names:             U.S. Robotics, Inc.

========================================================

Type of Work:      Visual Material

Registration Number / Date:
                   VA0000010366 / 1978-09-18 

Title:             USR-330 originate/auto-answer modem. C B T.

Description:       Schematic diagram.

Copyright Claimant:
                   U. S. Robotics, Inc.

Date of Creation:  1978

Date of Publication:
                   1978-01-03 

Names:             U.S. Robotics, Inc.

========================================================

Type of Work:      Visual Material

Registration Number / Date:
                   VA0000005432 / 1978-07-13 

Title:             USR-330 originate/auto-answer modem CBS.

Description:       Schematic diagram.

Copyright Claimant:
                   U. S. Robotics, Inc.

Date of Creation:  1978

Date of Publication:
                   1978-01-03 

Names:             U.S. Robotics, Inc.

========================================================