diff --git a/src/tools/DBD.pm b/src/tools/DBD.pm
index edc403811..20b149b85 100644
--- a/src/tools/DBD.pm
+++ b/src/tools/DBD.pm
@@ -29,22 +29,27 @@ sub new {
 
 sub add {
     my ($this, $obj) = @_;
-    my $obj_class;
-    foreach (keys %{$this}) {
-        next unless m/^DBD::/;
-        $obj_class = $_ and last if $obj->isa($_);
-    }
-    confess "Unknown object type"
-        unless defined $obj_class;
+    my $obj_class = ref $obj;
+    confess "DBD::add: Unknown DBD object type '$obj_class'"
+        unless $obj_class =~ m/^DBD::/
+        and exists $this->{$obj_class};
     my $obj_name = $obj->name;
-    dieContext("Duplicate name '$obj_name'")
-        if exists $this->{$obj_class}->{$obj_name};
-    $this->{$obj_class}->{$obj_name} = $obj;
+    if (exists $this->{$obj_class}->{$obj_name}) {
+        return if $obj->equals($this->{$obj_class}->{$obj_name});
+        dieContext("A different $obj->{WHAT} named '$obj_name' already exists");
+    }
+    else {
+        $this->{$obj_class}->{$obj_name} = $obj;
+    }
 }
 
 sub breaktables {
     return shift->{'DBD::Breaktable'};
 }
+sub breaktable {
+    my ($this, $name) = @_;
+    return $this->{'DBD::Breaktable'}->{$name};
+}
 
 sub drivers {
     return shift->{'DBD::Driver'};
diff --git a/src/tools/DBD/Base.pm b/src/tools/DBD/Base.pm
index 59602aab9..92b23a388 100644
--- a/src/tools/DBD/Base.pm
+++ b/src/tools/DBD/Base.pm
@@ -34,19 +34,19 @@ sub pushContext {
 
 sub popContext {
     my ($ctxt) = @_;
-    my ($pop) = shift @context;
+    my $pop = shift @context;
     ($ctxt ne $pop) and
-        dieContext("Exiting context \"$ctxt\", found \"$pop\" instead.",
-            "\tBraces must close in the same file they were opened.");
+        dieContext("Leaving context \"$ctxt\", found \"$pop\" instead.",
+            "\tBraces must be closed in the same file they open in.");
 }
 
 sub dieContext {
-    my ($msg) = join "\n\t", @_;
+    my $msg = join "\n\t", @_;
     die "$msg\nContext: ", join(' in ', @context), "\n";
 }
 
 sub warnContext {
-    my ($msg) = join "\n\t", @_;
+    my $msg = join "\n\t", @_;
     print STDERR "$msg\nContext: ", join(' in ', @context), "\n";
 }
 
@@ -77,7 +77,8 @@ sub is_reserved {
 sub identifier {
     my ($id, $what) = @_;
     unquote $id;
-    confess "$what undefined!" unless defined $id;
+    confess "DBD::Base::identifier: $what undefined!"
+        unless defined $id;
     $id =~ m/^$RXident$/o or dieContext("Illegal $what '$id'",
         "Identifiers are used in C code so must start with a letter, followed",
         "by letters, digits and/or underscore characters only.");
@@ -114,7 +115,8 @@ sub new {
 
 sub init {
     my ($this, $name, $what) = @_;
-    $this->{NAME} = identifier($name, $what);
+    $this->{NAME} = identifier($name, "$what name");
+    $this->{WHAT} = $what;
     return $this;
 }
 
@@ -122,4 +124,14 @@ sub name {
     return shift->{NAME};
 }
 
+sub what {
+    return shift->{WHAT};
+}
+
+sub equals {
+    my ($a, $b) = @_;
+    return $a->{NAME} eq $b->{NAME}
+        && $a->{WHAT} eq $b->{WHAT};
+}
+
 1;
diff --git a/src/tools/DBD/Breaktable.pm b/src/tools/DBD/Breaktable.pm
index 5199d61fb..8d2479834 100644
--- a/src/tools/DBD/Breaktable.pm
+++ b/src/tools/DBD/Breaktable.pm
@@ -5,23 +5,25 @@ use DBD::Base;
 use Carp;
 
 sub init {
-	my ($this, $name) = @_;
-	$this->SUPER::init($name, "breakpoint table name");
-        $this->{POINT_LIST} = [];
-        return $this;
+    my ($this, $name) = @_;
+    $this->SUPER::init($name, "breakpoint table");
+    $this->{POINT_LIST} = [];
+    return $this;
 }
 
 sub add_point {
-	my ($this, $raw, $eng) = @_;
-	confess "Raw value undefined!" unless defined $raw;
-	confess "Engineering value undefined!" unless defined $eng;
-	unquote $raw;
-	unquote $eng;
-	push @{$this->{POINT_LIST}}, [$raw, $eng];
+    my ($this, $raw, $eng) = @_;
+    confess "DBD::Breaktable::add_point: Raw value undefined!"
+        unless defined $raw;
+    confess "DBD::Breaktable::add_point: Engineering value undefined!"
+        unless defined $eng;
+    unquote $raw;
+    unquote $eng;
+    push @{$this->{POINT_LIST}}, [$raw, $eng];
 }
 
 sub points {
-	return @{shift->{POINT_LIST}};
+    return @{shift->{POINT_LIST}};
 }
 
 sub point {
@@ -29,4 +31,11 @@ sub point {
     return $this->{POINT_LIST}[$idx];
 }
 
+sub equals {
+    my ($a, $b) = @_;
+    return $a->SUPER::equals($b)
+        && join(',', map "$_->[0]:$_->[1]", @{$a->{POINT_LIST}})
+        eq join(',', map "$_->[0]:$_->[1]", @{$b->{POINT_LIST}});
+}
+
 1;
diff --git a/src/tools/DBD/Device.pm b/src/tools/DBD/Device.pm
index f439c6d86..72072e545 100644
--- a/src/tools/DBD/Device.pm
+++ b/src/tools/DBD/Device.pm
@@ -3,43 +3,50 @@ use DBD::Base;
 @ISA = qw(DBD::Base);
 
 my %link_types = (
-	CONSTANT  => qr/$RXnum/o,
-	PV_LINK   => qr/$RXname \s+ [.NPCAMS ]*/ox,
-	VME_IO    => qr/\# (?: \s* [CS] \s* $RXintx)* \s* (?: @ .*)?/ox,
-	CAMAC_IO  => qr/\# (?: \s* [BCNAF] \s* $RXintx)* \s* (?: @ .*)?/ox,
-	RF_IO     => qr/\# (?: \s* [RMDE] \s* $RXintx)*/ox,
-	AB_IO     => qr/\# (?: \s* [LACS] \s* $RXintx)* \s* (?: @ .*)?/ox,
-	GPIB_IO   => qr/\# (?: \s* [LA] \s* $RXintx)* \s* (?: @ .*)?/ox,
-	BITBUS_IO => qr/\# (?: \s* [LNPS] \s* $RXuintx)* \s* (?: @ .*)?/ox,
-	BBGPIB_IO => qr/\# (?: \s* [LBG] \s* $RXuintx)* \s* (?: @ .*)?/ox,
-	VXI_IO    => qr/\# (?: \s* [VCS] \s* $RXintx)* \s* (?: @ .*)?/ox,
-	INST_IO   => qr/@.*/
+    CONSTANT  => qr/$RXnum/o,
+    PV_LINK   => qr/$RXname \s+ [.NPCAMS ]*/ox,
+    VME_IO    => qr/\# (?: \s* [CS] \s* $RXintx)* \s* (?: @ .*)?/ox,
+    CAMAC_IO  => qr/\# (?: \s* [BCNAF] \s* $RXintx)* \s* (?: @ .*)?/ox,
+    RF_IO     => qr/\# (?: \s* [RMDE] \s* $RXintx)*/ox,
+    AB_IO     => qr/\# (?: \s* [LACS] \s* $RXintx)* \s* (?: @ .*)?/ox,
+    GPIB_IO   => qr/\# (?: \s* [LA] \s* $RXintx)* \s* (?: @ .*)?/ox,
+    BITBUS_IO => qr/\# (?: \s* [LNPS] \s* $RXuintx)* \s* (?: @ .*)?/ox,
+    BBGPIB_IO => qr/\# (?: \s* [LBG] \s* $RXuintx)* \s* (?: @ .*)?/ox,
+    VXI_IO    => qr/\# (?: \s* [VCS] \s* $RXintx)* \s* (?: @ .*)?/ox,
+    INST_IO   => qr/@.*/
 );
 
 sub init {
-	my ($this, $link_type, $dset, $choice) = @_;
-        unquote $choice;
-	dieContext("Unknown link type '$link_type', valid types are:",
-		sort keys %link_types) unless exists $link_types{$link_type};
-	$this->SUPER::init($dset, "DSET name");
-	$this->{LINK_TYPE} = $link_type;
-	$this->{CHOICE} = $choice;
-	return $this;
+    my ($this, $link_type, $dset, $choice) = @_;
+    unquote $choice;
+    dieContext("Unknown link type '$link_type', valid types are:",
+        sort keys %link_types) unless exists $link_types{$link_type};
+    $this->SUPER::init($dset, "device support (dset)");
+    $this->{LINK_TYPE} = $link_type;
+    $this->{CHOICE} = $choice;
+    return $this;
 }
 
 sub link_type {
-	return shift->{LINK_TYPE};
+    return shift->{LINK_TYPE};
 }
 
 sub choice {
-	return shift->{CHOICE};
+    return shift->{CHOICE};
 }
 
 sub legal_addr {
-        my ($this, $addr) = @_;
-        my $rx = $link_types{$this->{LINK_TYPE}};
-        unquote $addr;
-        return $addr =~ m/^ $rx $/x;
+    my ($this, $addr) = @_;
+    my $rx = $link_types{$this->{LINK_TYPE}};
+    unquote $addr;
+    return $addr =~ m/^ $rx $/x;
+}
+
+sub equals {
+    my ($a, $b) = @_;
+    return $a->SUPER::equals($b)
+        && $a->{LINK_TYPE} eq $b->{LINK_TYPE}
+        && $a->{CHOICE}    eq $b->{CHOICE};
 }
 
 1;
diff --git a/src/tools/DBD/Driver.pm b/src/tools/DBD/Driver.pm
index 7eedcdf8d..ddbae8f38 100644
--- a/src/tools/DBD/Driver.pm
+++ b/src/tools/DBD/Driver.pm
@@ -3,7 +3,7 @@ use DBD::Base;
 @ISA = qw(DBD::Base);
 
 sub init {
-    return shift->SUPER::init(shift, "driver entry table name");
+    return shift->SUPER::init(shift, "driver support (drvet)");
 }
 
 1;
diff --git a/src/tools/DBD/Function.pm b/src/tools/DBD/Function.pm
index 51e17d8aa..4a4a4cbfe 100644
--- a/src/tools/DBD/Function.pm
+++ b/src/tools/DBD/Function.pm
@@ -3,8 +3,7 @@ use DBD::Base;
 @ISA = qw(DBD::Base);
 
 sub init {
-    return shift->SUPER::init(shift, "function name");
+    return shift->SUPER::init(shift, "function");
 }
 
 1;
-
diff --git a/src/tools/DBD/Menu.pm b/src/tools/DBD/Menu.pm
index b8b1fb3d0..a7ca26ab9 100644
--- a/src/tools/DBD/Menu.pm
+++ b/src/tools/DBD/Menu.pm
@@ -4,7 +4,7 @@ use DBD::Base;
 
 sub init {
     my ($this, $name) = @_;
-    $this->SUPER::init($name, "menu name");
+    $this->SUPER::init($name, "menu");
     $this->{CHOICE_LIST} = [];
     $this->{CHOICE_INDEX} = {};
     return $this;
@@ -39,6 +39,13 @@ sub legal_choice {
     return exists $this->{CHOICE_INDEX}->{$value};
 }
 
+sub equals {
+    my ($a, $b) = @_;
+    return $a->SUPER::equals($b)
+        && join(',', map "$_->[0]:$_->[1]", @{$a->{CHOICE_LIST}})
+        eq join(',', map "$_->[0]:$_->[1]", @{$b->{CHOICE_LIST}});
+}
+
 sub toDeclaration {
     my $this = shift;
     my $name = $this->name;
diff --git a/src/tools/DBD/Output.pm b/src/tools/DBD/Output.pm
index 2f5cef657..b82ff98c9 100644
--- a/src/tools/DBD/Output.pm
+++ b/src/tools/DBD/Output.pm
@@ -48,7 +48,10 @@ sub OutputRecordtypes {
             printf $out "    field(%s, %s) {\n",
                 $field->name, $field->dbf_type;
             while (my ($attr, $val) = each %{$field->attributes}) {
-                $val = "\"$val\"" if $val !~ m/^$RXname$/ox;
+                $val = "\"$val\""
+                    if $val !~ m/^$RXname$/ox
+                       || $attr eq 'prompt'
+                       || $attr eq 'initial';
                 printf $out "        %s(%s)\n", $attr, $val;
             }
             print $out "    }\n";
diff --git a/src/tools/DBD/Parser.pm b/src/tools/DBD/Parser.pm
index c53c70e60..8cace9c17 100644
--- a/src/tools/DBD/Parser.pm
+++ b/src/tools/DBD/Parser.pm
@@ -49,7 +49,7 @@ sub ParseDBD {
         }
         elsif (m/\G variable \s* \( \s* $RXstr \s* \)/oxgc) {
             print "Variable: $1\n" if $debug;
-            $dbd->add(DBD::Variable->new($1, 'int'));
+            $dbd->add(DBD::Variable->new($1));
         }
         elsif (m/\G variable \s* \( \s* $RXstr \s* , \s* $RXstr \s* \)/oxgc) {
             print "Variable: $1, $2\n" if $debug;
@@ -59,7 +59,8 @@ sub ParseDBD {
                           \s* $RXstr \s* , \s*$RXstr \s* \)/oxgc) {
             print "Device: $1, $2, $3, $4\n" if $debug;
             my $rtyp = $dbd->recordtype($1);
-            dieContext("Unknown record type '$1'") unless defined $rtyp;
+            dieContext("Unknown record type '$1'")
+                unless defined $rtyp;
             $rtyp->add_device(DBD::Device->new($2, $3, $4));
         } else {
             last unless m/\G (.*) $/moxgc;
diff --git a/src/tools/DBD/Recfield.pm b/src/tools/DBD/Recfield.pm
index 259af0eb6..cdf8e2747 100644
--- a/src/tools/DBD/Recfield.pm
+++ b/src/tools/DBD/Recfield.pm
@@ -3,6 +3,7 @@ use DBD::Base;
 @ISA = qw(DBD::Base);
 
 # The hash value is a regexp that matches all legal values of this field
+# NB: The regexps are not currently used, and are wrong for some types.
 our %field_types = (
     DBF_STRING   => qr/.{0,40}/,
     DBF_CHAR     => $RXintx,
@@ -49,7 +50,7 @@ sub new {
 sub init {
     my ($this, $name, $type) = @_;
     unquote $type;
-    $this->SUPER::init($name, "record field name");
+    $this->SUPER::init($name, "record field");
     dieContext("Illegal field type '$type', valid field types are:",
         sort keys %field_types) unless exists $field_types{$type};
     $this->{DBF_TYPE} = $type;
@@ -91,6 +92,10 @@ sub attribute {
     return $this->attributes->{$attr};
 }
 
+sub equals {
+    dieContext("Record field objects are not comparable");
+}
+
 sub check_valid {
     my ($this) = @_;
     my $name = $this->name;
diff --git a/src/tools/DBD/Recordtype.pm b/src/tools/DBD/Recordtype.pm
index f6571b7e0..f730777a3 100644
--- a/src/tools/DBD/Recordtype.pm
+++ b/src/tools/DBD/Recordtype.pm
@@ -5,8 +5,8 @@ use DBD::Base;
 use Carp;
 
 sub init {
-    my $this = shift;
-    $this->SUPER::init(@_);
+    my ($this, $name) = @_;
+    $this->SUPER::init($name, "record type");
     $this->{FIELD_LIST} = [];
     $this->{FIELD_INDEX} = {};
     $this->{DEVICE_LIST} = [];
@@ -17,7 +17,8 @@ sub init {
 
 sub add_field {
     my ($this, $field) = @_;
-    confess "Not a DBD::Recfield" unless $field->isa('DBD::Recfield');
+    confess "DBD::Recordtype::add_field: Not a DBD::Recfield"
+        unless $field->isa('DBD::Recfield');
     my $field_name = $field->name;
     dieContext("Duplicate field name '$field_name'")
         if exists $this->{FIELD_INDEX}->{$field_name};
@@ -32,12 +33,7 @@ sub fields {
 }
 
 sub field_names { # In their original order...
-    my $this = shift;
-    my @names = ();
-    foreach ($this->fields) {
-        push @names, $_->name
-    }
-    return @names;
+    return map {$_->name} @{shift->{FIELD_LIST}};
 }
 
 sub field {
@@ -47,17 +43,18 @@ sub field {
 
 sub add_device {
     my ($this, $device) = @_;
-    confess "Not a DBD::Device" unless $device->isa('DBD::Device');
+    confess "DBD::Recordtype::add_device: Not a DBD::Device"
+        unless $device->isa('DBD::Device');
     my $choice = $device->choice;
     if (exists $this->{DEVICE_INDEX}->{$choice}) {
-        my @warning = ("Duplicate device type '$choice'");
+        return if $device->equals($this->{DEVICE_INDEX}->{$choice});
+        my @warning = ("Two $this->{NAME} device supports '$choice' conflict");
         my $old = $this->{DEVICE_INDEX}->{$choice};
         push @warning, "Link types differ"
-            if ($old->link_type ne $device->link_type);
+            if $old->link_type ne $device->link_type;
         push @warning, "DSETs differ"
-            if ($old->name ne $device->name);
-        warnContext(@warning);
-        return;
+            if $old->name ne $device->name;
+        dieContext(@warning);
     }
     push @{$this->{DEVICE_LIST}}, $device;
     $this->{DEVICE_INDEX}->{$choice} = $device;
@@ -85,6 +82,11 @@ sub toCdefs {
     return join("\n", shift->cdefs) . "\n\n";
 }
 
+sub equals {
+    my ($a, $b) = @_;
+    dieContext("Duplicate definition of record type '$a->{NAME}'");
+}
+
 sub toDeclaration {
     my $this = shift;
     my @fields = map {
diff --git a/src/tools/DBD/Registrar.pm b/src/tools/DBD/Registrar.pm
index b4692c596..29d12cd11 100644
--- a/src/tools/DBD/Registrar.pm
+++ b/src/tools/DBD/Registrar.pm
@@ -3,9 +3,7 @@ use DBD::Base;
 @ISA = qw(DBD::Base);
 
 sub init {
-    return shift->SUPER::init(shift, "registrar function name");
+    return shift->SUPER::init(shift, "registrar function");
 }
 
-
 1;
-
diff --git a/src/tools/DBD/Variable.pm b/src/tools/DBD/Variable.pm
index 8d02d64cd..87ea6d47a 100644
--- a/src/tools/DBD/Variable.pm
+++ b/src/tools/DBD/Variable.pm
@@ -18,7 +18,7 @@ sub init {
     exists $valid_types{$type} or
         dieContext("Unknown variable type '$type', valid types are:",
             sort keys %valid_types);
-    $this->SUPER::init($name, "variable name");
+    $this->SUPER::init($name, "variable");
     $this->{VAR_TYPE} = $type;
     return $this;
 }
@@ -33,4 +33,10 @@ sub iocshArg_type {
     return $valid_types{$this->{VAR_TYPE}};
 }
 
+sub equals {
+    my ($a, $b) = @_;
+    return $a->SUPER::equals($b)
+        && $a->{VAR_TYPE} eq $b->{VAR_TYPE};
+}
+
 1;