+ """
+ A CTF clock allows the description of the system's clock topology, as
+ well as the definition of each clock's parameters.
+
+ :class:`Clock` objects must be registered to a :class:`Writer`
+ object (see :meth:`Writer.add_clock`), as well as be registered to
+ a :class:`StreamClass` object (see :attr:`StreamClass.clock`).
+ """
+