diff --git a/PDP18B/pdp18b_lp.c b/PDP18B/pdp18b_lp.c
index 345c9382..58852ff8 100644
--- a/PDP18B/pdp18b_lp.c
+++ b/PDP18B/pdp18b_lp.c
@@ -91,6 +91,7 @@ int32 lp62_66 (int32 dev, int32 pulse, int32 dat);
 int32 lp62_iors (void);
 t_stat lp62_svc (UNIT *uptr);
 t_stat lp62_reset (DEVICE *dptr);
+t_stat lp62_attach (UNIT *uptr, CONST char *cptr);
 
 /* Type 62 LPT data structures
 
@@ -130,7 +131,7 @@ DEVICE lp62_dev = {
     "LPT", &lp62_unit, lp62_reg, lp62_mod,
     1, 10, 31, 1, 8, 8,
     NULL, NULL, &lp62_reset,
-    NULL, NULL, NULL,
+    NULL, &lp62_attach, NULL,
     &lp62_dib, DEV_DISABLE
     };
 
@@ -235,6 +236,14 @@ lp62_ovrpr = 0;                                         /* clear overprint */
 return SCPE_OK;
 }
 
+/* Attach routine */
+
+t_stat lp62_attach (UNIT *uptr, CONST char *cptr)
+{
+sim_switches |= SWMASK ('A');
+return attach_unit (uptr, cptr);
+}
+
 /* IORS routine */
 
 int32 lp62_iors (void)
@@ -482,6 +491,7 @@ t_stat lp647_attach (UNIT *uptr, CONST char *cptr)
 {
 t_stat reason;
 
+sim_switches |= SWMASK ('A');
 reason = attach_unit (uptr, cptr);
 lp647_err = (lp647_unit.flags & UNIT_ATT)? 0: 1;        /* clr/set error */
 return reason;
@@ -646,6 +656,7 @@ t_stat lp09_attach (UNIT *uptr, CONST char *cptr)
 {
 t_stat reason;
 
+sim_switches |= SWMASK ('A');
 reason = attach_unit (uptr, cptr);
 lp09_err = (lp09_unit.flags & UNIT_ATT)? 0: 1;          /* clr/set error */
 return reason;
@@ -694,6 +705,7 @@ int32 lp15_66 (int32 dev, int32 pulse, int32 dat);
 int32 lp15_iors (void);
 t_stat lp15_svc (UNIT *uptr);
 t_stat lp15_reset (DEVICE *dptr);
+t_stat lp15_attach (UNIT *uptr, CONST char *cptr);
 
 int32 lp15_updsta (int32 New);
 
@@ -736,7 +748,7 @@ DEVICE lp15_dev = {
     "LPT", &lp15_unit, lp15_reg, lp15_mod,
     1, 10, 31, 1, 8, 8,
     NULL, NULL, &lp15_reset,
-    NULL, NULL, NULL,
+    NULL, &lp15_attach, NULL,
     &lp15_dib, DEV_DISABLE
     };
 
@@ -878,6 +890,14 @@ lp15_updsta (0);                                        /* update status */
 return SCPE_OK;
 }
 
+/* Attach routine */
+
+t_stat lp15_attach (UNIT *uptr, CONST char *cptr)
+{
+sim_switches |= SWMASK ('A');
+return attach_unit (uptr, cptr);
+}
+
 /* IORS routine */
 
 int32 lp15_iors (void)
diff --git a/PDP18B/pdp18b_stddev.c b/PDP18B/pdp18b_stddev.c
index 2dcc9f17..c47ceb76 100644
--- a/PDP18B/pdp18b_stddev.c
+++ b/PDP18B/pdp18b_stddev.c
@@ -650,9 +650,11 @@ return ((TST_INT (PTR)? IOS_PTR: 0)
 t_stat ptr_attach (UNIT *uptr, CONST char *cptr)
 {
 t_stat reason;
+int32 saved_switches = sim_switches;
 
-sim_switches |= SWMASK ('R');
+sim_switches &= ~SWMASK ('A');
 reason = attach_unit (uptr, cptr);
+sim_switches = saved_switches;
 if (reason != SCPE_OK)
     return reason;
 ptr_err = 0;                                             /* attach clrs error */
@@ -969,10 +971,13 @@ return SCPE_OK;
 t_stat ptp_attach (UNIT *uptr, CONST char *cptr)
 {
 t_stat reason;
+int32 saved_switches = sim_switches;
 
+sim_switches |= SWMASK ('A');   /* Default to Append to existing file */
 reason = attach_unit (uptr, cptr);
 if (reason != SCPE_OK)
     return reason;
+sim_switches = saved_switches;
 ptp_err = 0;
 ptp_unit.flags = ptp_unit.flags & ~UNIT_PASCII;
 if (sim_switches & SWMASK ('A'))
diff --git a/doc/pdp18b_doc.doc b/doc/pdp18b_doc.doc
index d23c1ccb..34e11779 100644
Binary files a/doc/pdp18b_doc.doc and b/doc/pdp18b_doc.doc differ