This file is from Wikimedia Commons and may be used by other projects.
The description on its file description page there is shown below.
Summary
Description1st order type 1 loop.png
English: 3 examples of block diagrams of 1st order type 1 Phase-locked loops intended for use inside CDR circuits. The Laplace transfer equation of every block is present. Capitals for the Laplace Transforms; identification of the error signal.
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.