diff --git a/6502/C64/src/vf-sys-c16.fth b/6502/C64/src/vf-sys-c16.fth
index 3dd8d44..4c74e42 100644
--- a/6502/C64/src/vf-sys-c16.fth
+++ b/6502/C64/src/vf-sys-c16.fth
@@ -9,8 +9,6 @@ include vf-lbls-cbm.fth
 0ff4c >label ConOut
   090 >label IOStatus
   09a >label MsgFlg
-  099 >label OutDev
-  098 >label  InDev
 0ff19 >label BrdCol
 0ff15 >label BkgCol
  053b >label PenCol
diff --git a/6502/C64/src/vf-sys-c64.fth b/6502/C64/src/vf-sys-c64.fth
index 9eb05de..10e0082 100644
--- a/6502/C64/src/vf-sys-c64.fth
+++ b/6502/C64/src/vf-sys-c64.fth
@@ -9,8 +9,6 @@ include vf-lbls-cbm.fth
 0E716 >label ConOut
   090 >label IOStatus
   09d >label MsgFlg
-  09a >label OutDev
-  099 >label  InDev
 0d020 >label BrdCol
 0d021 >label BkgCol
  0286 >label PenCol
diff --git a/6502/C64/src/vf-sys-cbm.fth b/6502/C64/src/vf-sys-cbm.fth
index 260a63e..44a9d28 100644
--- a/6502/C64/src/vf-sys-cbm.fth
+++ b/6502/C64/src/vf-sys-cbm.fth
@@ -100,7 +100,7 @@ Output: display   [ here output ! ]
 87 fthpage
 
 Code i/o-status?  ( -- n )
-  IOStatus lda  Push0A jmp  end-code
+  READST jsr  Push0A jmp  end-code
 
 \ b/blk drive >drive drvinit  clv14:2x87
 
@@ -131,7 +131,12 @@ Variable (drv    0 (drv !
 
 Variable i/o  0 i/o !  \ Semaphore
 
-Code busoff  ( --)   CLRCHN jsr
+Label LsnDev 0 c,
+Label TlkDev 0 c,
+
+Code busoff  ( --)
+ LsnDev lda  0<> ?[ LsnDev stx  UNLSN jsr ]?
+ TlkDev lda  0<> ?[ TlkDev stx  UNTLK jsr ]?
 Label unlocki/o  1 # ldy  0 # ldx
  ;c:  i/o unlock ;
 
@@ -164,7 +169,7 @@ Label (?dev
  N 2+ lda  (?dev jsr
  N 2+ lda  LISTEN jsr
  N lda  60 # ora SECOND jsr
- N 2+ ldx  OutDev stx
+ N 2+ ldx  LsnDev stx
  xyNext jmp  end-code
 
 
@@ -188,8 +193,7 @@ Label (?dev
  N 2+ lda  TALK jsr
  N lda  60 # ora (C16 $ad sta ( )
  TKSA jsr
-\ because of error in old C16 OS
- N 2+ ldx  InDev stx
+ N 2+ ldx  TlkDev stx
  xyNext jmp end-code
 
 : busin  ( dev 2nd -- )
diff --git a/6502/C64/src/vf-sys-x16.fth b/6502/C64/src/vf-sys-x16.fth
index 18cbc7e..b472e7d 100644
--- a/6502/C64/src/vf-sys-x16.fth
+++ b/6502/C64/src/vf-sys-x16.fth
@@ -9,8 +9,6 @@ include vf-lbls-cbm.fth
 0febd >label KbdbufPeek
  0289 >label IOStatus
  028c >label MsgFlg
- 028e >label OutDev
- 028d >label  InDev
 09f2c >label BrdCol
  0266 >label BkgCol
  0284 >label PenCol