diff --git a/site_ansto/instrument/sans/config/velsel/sct_velsel.tcl b/site_ansto/instrument/sans/config/velsel/sct_velsel.tcl
index 15f378ce..6ecea765 100644
--- a/site_ansto/instrument/sans/config/velsel/sct_velsel.tcl
+++ b/site_ansto/instrument/sans/config/velsel/sct_velsel.tcl
@@ -155,7 +155,7 @@ proc rdPwdAck {} {
 ##
 # @brief Request a state report from the velocity selector
   proc getStatus {} {
-    sct send "#SOS#STATE "
+    sct send "N#SOS#STATE "
     return rdState
   }
 
@@ -172,7 +172,7 @@ proc rdPwdAck {} {
     if {[string match {*#SES#You are not a valid user*} $staterep]} {
        return sendUID
     }
-    if {[string match {#SOS#*} $staterep] == 0 } {
+    if {[string match {N#SOS#*} $staterep] == 0 } {
       hset $root/device_error $staterep
       return idle
     }
@@ -256,7 +256,7 @@ proc rdPwdAck {} {
     variable paramindex
     set speed [format "%5d" [sct target]] 
 
-    sct send "#SOS#SPEED $speed"
+    sct send "N#SOS#SPEED $speed"
     set angle [lindex [hval $statuspath] $paramindex(ttang) end]
     set lambda [AngleSpeedToWavelength $angle $speed]
     sct target $speed
@@ -276,13 +276,13 @@ proc rdPwdAck {} {
     set state [string tolower [sct target]] 
       switch $state {
         "idle" {
-          sct send "#SOS#IDLE  "
+          sct send "N#SOS#IDLE  "
         }
         "brake" {
-          sct send "#SOS#BRAKE "
+          sct send "N#SOS#BRAKE "
         }
         "init" {
-          sct send "#SOS#TTINIT"
+          sct send "N#SOS#TTINIT"
         }
         default {
 					return idle
@@ -297,7 +297,11 @@ proc rdPwdAck {} {
 
     set angle [lindex [hval $statuspath] $paramindex(ttang) end]
     set aspeed [lindex [hval $statuspath] $paramindex(aspeed) end]
-    set lambda [AngleSpeedToWavelength $angle $aspeed]
+    if {$aspeed >= 3100} {
+      set lambda [AngleSpeedToWavelength $angle $aspeed]
+    } else {
+      set lambda 99999
+    }
     if {$lambda != [sct oldval]} {
       sct oldval $lambda
       sct update $lambda
@@ -416,7 +420,7 @@ proc halt {root} {
 
   proc setPar {par nextState} {
     set val [sct target]
-    sct send "#SOS#$par $val"
+    sct send "N#SOS#$par $val"
     return $nextState
   }
 
@@ -427,7 +431,7 @@ proc halt {root} {
     set angle [lindex [hval $statuspath] $paramindex(ttang) end]
     set speed [WavelengthToSpeed $angle $lambda]
     set fmtspeed [format "%5d" $speed] 
-    sct send "#SOS#SPEED $fmtspeed"
+    sct send "N#SOS#SPEED $fmtspeed"
     sct target $lambda
     hsetprop $vs_root/setspeed target $speed
     hset $vs_root/status "busy"