diff --git a/doc/master/handle_external_signal b/doc/master/handle_external_signal
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+++ b/doc/master/handle_external_signal
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+SYNOPSIS
+        #include <signals.h>
+
+        int handle_external_signal(int signal)
+
+DESCRIPTION
+        If the driver receives a signal from the OS it forwards it to the
+        mudlib master by calling this function. The signal received by the
+        driver is given in <signal> and may be one of the following:
+        SIGHUP, SIGINT, SIGTERM, SIGUSR1, SIGUSR2.
+
+        If this function returns != 0, the driver will assume the signal has
+        been dealt with and take NO further action.
+        The exception is SIGTERM, which can't be handled. The driver will
+        perform a graceful shutdown of the game after this function returns.
+
+        If the master does not handle the signal (returns 0 or this function
+        doe not exit), the driver will perform the following default actions:
+
+        SIGHUP:  begin a graceful shutdown
+        SIGINT:  send itself an unhandled SIGINT. This usually causes an
+                 immediate and non-graceful shutdown.
+        SIGUSR1: the driver will reload the master object
+        SIGUSR2: the driver will re-open its debug log file
+                 (this will happen the next time the driver writes to it)
+