1 files changed, 1 insertions, 0 deletions
diff --git a/bus.h b/bus.h
index f13f203..c72aacb 100644
--- a/bus.h
+++ b/bus.h
@@ -18,6 +18,7 @@
 #define O_GATE 3                /* gates output */
 #define OUTPUT_RELAY 4          /* output enable/disable relay */
 #define PW_ENABLE 5             /* TTL enable/disable output */
+#define POWER_FAIL 6		/* pulled low if +24V OK, pulled high if power fails */
 
 // A5, A6 used to select chips
 #define Octal_DACportCS_low	0x00