600 setwidth
1.5 setformat
-2.53 2.4 setxrange
pictpointsOff

/resolution 500 def

%% echelle semi-ln
/xscale {
   ln 
} def

.08 11 setxrange
-45 40 setyrange

%% la legende
<tex>
$$
   20 {\rm log} \left| {1\over 1 + 2jm {\omega \over \omega _0} +
   \left( j {\omega \over \omega _0}\right)^2}\right|
$$
</tex>
.12 25 [1.2 dup] urtexlabel

setSymbol
   (w/w) 8 -40 dctext 
   (0) indice

%% la numerotation
/ymarkstyle {(-5 0) bltext} def
.1 -40 setorigine
[.1 .2 1 2 10] 
{xmark} apply
10 setymkstep
ymarks
0 ymark

.1 10 setxrange
-40 40 setyrange
masque

gsave
.4 setgray
.4 setlinewidth
%% les verticales
[-1 1 log_seq] {svrule} apply

%% les horizontales
[-40 40 5 stepto] {shrule} apply
grestore

1 setlinewidth
%% la fonction a tracer
/f {
   setxvar
   1 0
   1 0
   0 x m mul 2 mul 
   addc
   0 x dupp mulc addc
   divc
   module
   log 20 mul
} def

/u {.5 0} def    %% vecteur pour les traits de legende

%% la courbe no 1
/m .01 def
.1 1 {f} Courbe
1 xmax {f} Courbe
%% et sa legende
1 dup f dupp point
dupp u translatepoint /A defpoint
A 1 trait
<tex>
   $m = 0, 01$
</tex>
A [1.2 dup] brtexlabel

bleu
%% la courbe no 2
/m .05 def
{f} courbe
1 dup f dupp point
dupp u translatepoint /A defpoint
A 1 trait
<tex>
   $m = 0, 05$
</tex>
A [1.2 dup] brtexlabel

orange
%% la courbe no 3
/m .1 def
{f} courbe
1 dup f dupp point
dupp u translatepoint /A defpoint
A 1 trait
<tex>
   $m = 0, 1$
</tex>
A [1.2 dup] brtexlabel

noir
%% la courbe no 4
/m .5 def
{f} courbe
1 dup f dupp point
dupp u translatepoint /A defpoint
A 1 trait
<tex>
   $m = 0, 5$
</tex>
A [1.2 dup] brtexlabel

/u {1.5 0} def

bleu
%% la courbe no 5
/m .707 def
{f} courbe
1 dup f dupp point
dupp u translatepoint /A defpoint
A 1 trait
<tex>
   $m = 0, 707$
</tex>
A [1.2 dup] brtexlabel

orange
%% la courbe no 6
/m 1 def
{f} courbe
1 dup f dupp point
dupp u translatepoint /A defpoint
A 1 trait
<tex>
   $m = 1$
</tex>
A [1.2 dup] brtexlabel

/u {-.3 -10} def

noir
%% la courbe no 7
/m 2 def
{f} courbe
1 dup f dupp point
dupp u translatepoint /A defpoint
A 1 trait
<tex>
   $m = 2$
</tex>
A [1.2 dup] dltexlabel

bleu 
%% la courbe no 8
/m 5 def
{f} courbe
1 dup f dupp point
dupp u translatepoint /A defpoint
A 1 trait
<tex>
   $m = 5$
</tex>
A [1.2 dup] dltexlabel