diff --git a/day20/sol.tcl b/day20/sol.tcl
index f6d61a5..d10c52d 100755
--- a/day20/sol.tcl
+++ b/day20/sol.tcl
@@ -6,6 +6,7 @@ proc read-input input {
     global type
     global flip
     global conj
+    global when
     while {[gets $input line] >= 0} {
         # oops
         set line [replace $line ">" > "&" &]
@@ -20,6 +21,7 @@ proc read-input input {
         } elseif {$sigil eq "&"} {
             set type($name) "conj"
             set conj($name) [dict create]
+            set when($name) [dict create]
         } else {
             error "unknown sigil $sigil"
         }
@@ -31,18 +33,20 @@ proc read-input input {
             }
             if {$type($to) eq "conj"} {
                 dict set conj($to) $n 0
+                dict set when($to) $n 0
             }
         }
     }
 }
 
 
-proc pulse {init {debug 0}} {
+proc pulse {init i {debug 0}} {
     global next
     global type
     global flip
     global conj
     global count
+    global when
 
     set n $init
     set pulses {}
@@ -78,6 +82,10 @@ proc pulse {init {debug 0}} {
                 }
                 conj {
                     dict set conj($n) $from $value
+                    # remember the last time we saw a high bit from each input
+                    if {$value} {
+                        dict set when($n) $from $i
+                    }
                     set all 1
                     foreach v [dict values $conj($n)] {
                         if {!$v} {
@@ -106,12 +114,13 @@ proc solve input {
     set count(0) 0
     set count(1) 0
 
-    global solved
-    set solved 0
+    global when
+    set last $when(dn)
     for {set i 1} {$i <= 1000} {incr i} {
-        pulse broadcaster
-        if {$solved} {
-            puts "rx $i"
+        pulse broadcaster $i
+        if {$when(dn) ne $last} {
+            puts $when(dn)
+            set last $when(dn)
         }
     }
 
@@ -122,16 +131,13 @@ proc solve input {
     global type
     if {![info exists type(rx)]} return
 
-    while {!$solved} {
-        pulse broadcaster
+    while {1} {
+        pulse broadcaster $i
+        if {$when(dn) ne $last} {
+            puts $when(dn)
+            set last $when(dn)
+        }
         incr i
-        if {$solved} {
-            puts "rx $i"
-            break
-        }
-        if {$i % 1000 == 0} {
-            puts "\[$i\]"
-        }
     }
 }