mass changes; fix titles; add examples; correct typos; clarifications;
unified style; etc.
diff --git a/Doc/lib/libsignal.tex b/Doc/lib/libsignal.tex
index 13139d7..63b671f 100644
--- a/Doc/lib/libsignal.tex
+++ b/Doc/lib/libsignal.tex
@@ -20,7 +20,7 @@
``atomic'' instructions of the Python interpreter. This means that
signals arriving during long calculations implemented purely in C
(e.g.\ regular expression matches on large bodies of text) may be
-delayed for an arbitrary time.
+delayed for an arbitrary amount of time.
\item
When a signal arrives during an I/O operation, it is possible that the
@@ -48,8 +48,10 @@
in the main thread of execution. Any thread can perform an
\code{alarm()}, \code{getsignal()}, or \code{pause()}; only the main
thread can set a new signal handler, and the main thread will be the
-only one to receive signals. This means that signals can't be used as
-a means of interthread communication. Use locks instead.
+only one to receive signals (this is enforced by the Python signal
+module, even if the underlying thread implementation supports sending
+signals to individual threads). This means that signals can't be used
+as a means of interthread communication. Use locks instead.
\end{itemize}
@@ -126,4 +128,9 @@
When threads are enabled, this function can only be called from the
main thread; attempting to call it from other threads will cause a
\code{ValueError} exception to be raised.
+
+ The \var{handler} is called with two arguments: the signal number
+ and the current stack frame (\code{None} or a frame object; see the
+ reference manual for a description of frame objects).
+\obindex{frame}
\end{funcdesc}