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diff --git a/src/c2espcommon.c b/src/c2espcommon.c
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index 51291f7..409e7f6 100644
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--- a/src/c2espcommon.c
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+++ b/src/c2espcommon.c
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@@ -43,11 +43,11 @@
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  * Globals...
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  */
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 char		CallerName[50];  	/* String that identifies the calling program */
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-int		DoBack;			/* Enables the back channel comms */ 
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+extern int	DoBack;			/* Enables the back channel comms */
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 char 		BackBuf[32000]; //for the back channel replies from the printer
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 int 		BackBufLen=sizeof(BackBuf)-1;
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 FILE 		*LogFile = NULL; //file descriptor for log file
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-time_t		StartTime;
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+extern time_t	StartTime;
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 int		BlackPercent, ColourPercent;
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 time_t KeepAwake(time_t Start, int Interval, FILE *PrintFile)
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diff --git a/src/c2espcommon.h b/src/c2espcommon.h
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index b726204..967e9ce 100644
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--- a/src/c2espcommon.h
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+++ b/src/c2espcommon.h
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@@ -35,8 +35,8 @@
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 /*
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  * Globals...
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 */
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-char 		BackBuf[32000]; //for the back channel replies from the printer
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-int		ColourPercent, BlackPercent; //to store the detected marker levels
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+extern char 	BackBuf[32000]; //for the back channel replies from the printer
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+extern int	ColourPercent, BlackPercent; //to store the detected marker levels
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 time_t KeepAwake(time_t Start, int Interval, FILE *PrintFile);