solidbrush 255 255 255
solidpen 0 255 0 0
//roundrect 0 0 60 40 5 5 
solidpen 0 255  0 0 
moveto 3 0
lineto 3 40
moveto 0 37
lineto 60 37
solidpen 128 128 128   0 
moveto 3 37
lineto 6 20
lineto  9 33
lineto 12 17
lineto 15 30
lineto 18  12
lineto 21 27
lineto 24 9
lineto 27 27
lineto 30 9
lineto 33 27
lineto 36 9
lineto 39 27
lineto 42 9
lineto 45 27
lineto 48 9
lineto 51 27
lineto 53 9
lineto 56 27
lineto 59 9
// averaged line
solidpen 255 0 0 3
moveto 20  20
lineto 40 20
// borders
solidpen 255 0 0 1
moveto 20  10
lineto 20 40
moveto 40  10
lineto 40 40
label 30 40 Δt
// ingang
moveto -15 15
lineto -7 7
moveto -7 15
lineto -15 7
//moveto -15 5
//lineto -7 5
// uitgang
moveto 65 15
lineto 73 7
moveto 73 15
lineto 65 7
moveto 65 5
lineto 73 5