A block diagram showing usage of the abbreviation trafo instead of transformer.
The file was copied (with modifications) from: Hans DeVries, Suresh Ramamurthi, Facsimile modem for passing image information to a facsimile machine and computer, 1997, US Patent US5617221
trafo_patent.png
You can use this image freely, but you must give the following credits:
original source: United States Patent and Trademark Office, license: Public Domain
Copyright law (17 U.S.C. § 105) states that all materials created by the United States government are in the public domain. However, there are restrictions on use. Anyone incorporating a work of the U.S. Government into a copyrighted work should be aware of 17 U.S.C. § 403. This section requires a copyright notice to contain a statement identifying what portions of the work consist of a work of the U.S.Government. Failure to do so could result in loss of copyright protection for the entire work.