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diff --git a/diagrams/chassis-dimensional-requirements.typ b/diagrams/chassis-dimensional-requirements.typ
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+++ b/diagrams/chassis-dimensional-requirements.typ
@@ -0,0 +1,477 @@
+#import "../lib/unify.typ": qty
+#import "@preview/cetz:0.5.2"
+
+#figure(
+  cetz.canvas({
+    import cetz.draw: *
+
+    // Scale factor: 1 mm = 0.04 drawing units
+    let s = 0.04
+
+    // =========================================================================
+    // VIEW A: SIDE ELEVATION CUTAWAY (Chassis & Module Clearance)
+    // =========================================================================
+    let x-side-start = -3.8
+    let y-side-bot = 0
+    let h-panel = 177.8 * s // 4.2672
+    let h-body = 165.1 * s // 3.9624
+    let h-lip = 6.35 * s // 0.1524
+    let d-body = 152.4 * s // 3.6576
+    let d-cable = 28.0 * s // 0.672 (>= 25 mm cable bend zone)
+
+    let y-side-top = y-side-bot + h-panel
+    let y-body-bot = y-side-bot + h-lip
+    let y-body-top = y-side-top - h-lip
+    let x-panel-front = x-side-start
+    let x-body-start = x-panel-front + 3.0 * s
+    let x-body-rear = x-body-start + d-body
+    let x-chassis-rear = x-body-rear + d-cable
+
+    // View Title
+    content((x-body-start + (d-body + d-cable) / 2, y-side-top + 1.5), text(
+      size: 8.5pt,
+      weight: "bold",
+    )[VIEW A: SIDE ELEVATION CUTAWAY])
+    content((x-body-start + (d-body + d-cable) / 2, y-side-top + 1.15), text(
+      size: 7pt,
+      fill: luma(90),
+    )[(Chassis enclosure & module interface clearance)])
+
+    // Chassis Steel Structure Outline (1.5 mm / 2.0 mm outer shell)
+    rect(
+      (x-body-start - 2.0 * s, y-side-bot - 2.0 * s),
+      (x-chassis-rear + 2.0 * s, y-side-top + 2.0 * s),
+      fill: luma(250),
+      stroke: 1.2pt + black,
+    )
+
+    // Cassette Guide Rails (Top and Bottom Channels)
+    rect(
+      (x-body-start, y-side-top - 8.0 * s),
+      (x-body-rear, y-side-top),
+      fill: luma(210),
+      stroke: 0.8pt + black,
+    )
+    rect(
+      (x-body-start, y-side-bot),
+      (x-body-rear, y-side-bot + 8.0 * s),
+      fill: luma(210),
+      stroke: 0.8pt + black,
+    )
+
+    // Installed Cassette Outer Body (White fill inside chassis)
+    rect(
+      (x-body-start, y-body-bot),
+      (x-body-rear, y-body-top),
+      fill: white,
+      stroke: 1pt + black,
+    )
+
+    // Front Panel Attached to Cassette Lip
+    rect(
+      (x-panel-front, y-side-bot),
+      (x-body-start, y-side-top),
+      fill: luma(225),
+      stroke: 1.2pt + black,
+    )
+
+    // DB-25 Backplane Connector (Mating Pair at Rear of Cassette)
+    let db-h = 50.0 * s
+    rect(
+      (x-body-rear - 2.0 * s, y-side-bot + (h-panel - db-h) / 2),
+      (x-body-rear + 8.0 * s, y-side-bot + (h-panel + db-h) / 2),
+      fill: luma(180),
+      stroke: 0.9pt + black,
+    )
+
+    // Cable Bend & Wiring Harness Zone (Dashed hatched path behind backplane)
+    line(
+      (x-body-rear + 8.0 * s, y-side-bot + h-panel / 2),
+      (x-chassis-rear - 4.0 * s, y-side-bot + h-panel / 2),
+      (x-chassis-rear - 4.0 * s, y-side-bot + 15.0 * s),
+      stroke: (paint: luma(120), thickness: 0.8pt, dash: "dashed"),
+    )
+
+    // Dimensions for View A
+    // Total Panel Height (177.8 mm / 4U)
+    line(
+      (x-panel-front, y-side-bot),
+      (x-panel-front - 0.5, y-side-bot),
+      stroke: 0.4pt + luma(140),
+    )
+    line(
+      (x-panel-front, y-side-top),
+      (x-panel-front - 0.5, y-side-top),
+      stroke: 0.4pt + luma(140),
+    )
+    line(
+      (x-panel-front - 0.45, y-side-bot),
+      (x-panel-front - 0.45, y-side-top),
+      mark: (start: "stealth", end: "stealth"),
+      mark-size: 0.08,
+      stroke: 0.6pt + black,
+    )
+    content(
+      (x-panel-front - 0.75, (y-side-bot + y-side-top) / 2),
+      text(size: 6.5pt, weight: "bold")[$qty(177.8, "mm")$ ($qty(4, "U")$)],
+      angle: 90deg,
+    )
+
+    // Lip Height (6.35 mm)
+    line(
+      (x-body-start, y-side-top),
+      (x-body-start + 0.4, y-side-top),
+      stroke: 0.4pt + luma(140),
+    )
+    line(
+      (x-body-start, y-body-top),
+      (x-body-start + 0.4, y-body-top),
+      stroke: 0.4pt + luma(140),
+    )
+    line(
+      (x-body-start + 0.35, y-body-top),
+      (x-body-start + 0.35, y-side-top),
+      mark: (start: "stealth", end: "stealth"),
+      mark-size: 0.06,
+      stroke: 0.6pt + black,
+    )
+    content((x-body-start + 0.65, (y-body-top + y-side-top) / 2), text(
+      size: 5.5pt,
+    )[$qty(6.35, "mm")$])
+
+    // Body Height (165.1 mm)
+    line(
+      (x-body-start + 0.8, y-body-bot),
+      (x-body-start + 0.8, y-body-top),
+      stroke: (paint: luma(140), thickness: 0.4pt, dash: "dashed"),
+    )
+    line(
+      (x-body-start + 0.8, y-body-bot),
+      (x-body-start + 0.8, y-body-top),
+      mark: (start: "stealth", end: "stealth"),
+      mark-size: 0.08,
+      stroke: 0.6pt + black,
+    )
+    content(
+      (x-body-start + 1.1, (y-body-bot + y-body-top) / 2),
+      text(size: 6.5pt)[$qty(165.1, "mm")$ body],
+      angle: -90deg,
+    )
+
+    // Cassette Depth (152.4 mm)
+    line(
+      (x-body-start, y-side-top + 2.0 * s),
+      (x-body-start, y-side-top + 0.5),
+      stroke: 0.4pt + luma(140),
+    )
+    line(
+      (x-body-rear, y-side-top + 2.0 * s),
+      (x-body-rear, y-side-top + 0.5),
+      stroke: 0.4pt + luma(140),
+    )
+    line(
+      (x-body-start, y-side-top + 0.45),
+      (x-body-rear, y-side-top + 0.45),
+      mark: (start: "stealth", end: "stealth"),
+      mark-size: 0.08,
+      stroke: 0.6pt + black,
+    )
+    content(((x-body-start + x-body-rear) / 2, y-side-top + 0.65), text(
+      size: 6.5pt,
+    )[$qty(152.4, "mm")$])
+
+    // Cable Zone Depth (>= 25.0 mm)
+    line(
+      (x-chassis-rear, y-side-top + 2.0 * s),
+      (x-chassis-rear, y-side-top + 0.5),
+      stroke: 0.4pt + luma(140),
+    )
+    line(
+      (x-body-rear, y-side-top + 0.45),
+      (x-chassis-rear, y-side-top + 0.45),
+      mark: (start: "stealth", end: "stealth"),
+      mark-size: 0.08,
+      stroke: 0.6pt + black,
+    )
+    content(((x-body-rear + x-chassis-rear) / 2, y-side-top + 0.65), text(
+      size: 6pt,
+    )[$gt.eq qty(25.0, "mm")$])
+
+    // Callout Annotations for View A
+    line(
+      (x-body-rear + 3.0 * s, y-side-bot + h-panel / 2),
+      (x-body-rear + 1.2, y-side-bot + h-panel / 2 + 0.6),
+      stroke: 0.5pt + black,
+    )
+    content(
+      (x-body-rear + 1.25, y-side-bot + h-panel / 2 + 0.6),
+      text(size: 6pt)[DB-25 backplane \
+        (grounded via shell & pin 25)],
+      anchor: "south-west",
+    )
+
+    line(
+      (x-chassis-rear - 2.0 * s, y-side-bot + 20.0 * s),
+      (x-chassis-rear + 0.5, y-side-bot - 0.3),
+      stroke: 0.5pt + black,
+    )
+    content(
+      (x-chassis-rear + 0.55, y-side-bot - 0.3),
+      text(size: 6pt)[Cable bend & wiring zone],
+      anchor: "west",
+    )
+
+    // =========================================================================
+    // VIEW B: FRONT ELEVATION (Module Pitch Alignment)
+    // =========================================================================
+    let x-front-view = 7.2
+    let w-module = 38.0 * s // 0.912
+    let pitch-module = 38.1 * s // 0.9144
+
+    // View Title
+    content((x-front-view + 1.5 * pitch-module, y-side-top + 1.5), text(
+      size: 8.5pt,
+      weight: "bold",
+    )[VIEW B: FRONT ELEVATION])
+    content((x-front-view + 1.5 * pitch-module, y-side-top + 1.15), text(
+      size: 7pt,
+      fill: luma(90),
+    )[(Module pitch & slot interface alignment)])
+
+    // Chassis Front Frame
+    rect(
+      (x-front-view - 0.2, y-side-bot - 2.0 * s),
+      (x-front-view + 3 * pitch-module + 0.2, y-side-top + 2.0 * s),
+      fill: luma(240),
+      stroke: 1.2pt + black,
+    )
+
+    // Module Slot 1 (Module 1 Installed)
+    let m1-x = x-front-view
+    rect(
+      (m1-x, y-side-bot),
+      (m1-x + w-module, y-side-top),
+      fill: luma(250),
+      stroke: 1pt + black,
+    )
+    circle(
+      (m1-x + w-module / 2, y-side-bot + h-lip / 2),
+      radius: 1.2 * s,
+      fill: white,
+      stroke: 0.6pt + black,
+    )
+    circle(
+      (m1-x + w-module / 2, y-side-top - h-lip / 2),
+      radius: 1.2 * s,
+      fill: white,
+      stroke: 0.6pt + black,
+    )
+    content((m1-x + w-module / 2, y-side-bot + h-panel / 2), text(
+      size: 6.5pt,
+      weight: "bold",
+    )[Module 1])
+
+    // Module Slot 2 (Module 2 Installed)
+    let m2-x = x-front-view + pitch-module
+    rect(
+      (m2-x, y-side-bot),
+      (m2-x + w-module, y-side-top),
+      fill: luma(250),
+      stroke: 1pt + black,
+    )
+    circle(
+      (m2-x + w-module / 2, y-side-bot + h-lip / 2),
+      radius: 1.2 * s,
+      fill: white,
+      stroke: 0.6pt + black,
+    )
+    circle(
+      (m2-x + w-module / 2, y-side-top - h-lip / 2),
+      radius: 1.2 * s,
+      fill: white,
+      stroke: 0.6pt + black,
+    )
+    content((m2-x + w-module / 2, y-side-bot + h-panel / 2), text(
+      size: 6.5pt,
+      weight: "bold",
+    )[Module 2])
+
+    // Module Slot 3 (Empty Slot showing chassis guide rails)
+    let m3-x = x-front-view + 2 * pitch-module
+    rect(
+      (m3-x, y-side-bot),
+      (m3-x + w-module, y-side-top),
+      fill: white,
+      stroke: 0.8pt + black,
+    )
+    rect(
+      (m3-x, y-side-top - h-lip),
+      (m3-x + w-module, y-side-top),
+      fill: luma(210),
+      stroke: 0.5pt + black,
+    )
+    rect(
+      (m3-x, y-side-bot),
+      (m3-x + w-module, y-side-bot + h-lip),
+      fill: luma(210),
+      stroke: 0.5pt + black,
+    )
+    content((m3-x + w-module / 2, y-side-bot + h-panel / 2), text(
+      size: 6pt,
+      fill: luma(100),
+    )[Empty slot \ (rails visible)])
+
+    // Centerlines for Module Center Pitch
+    line(
+      (m1-x + w-module / 2, y-side-bot - 0.4),
+      (m1-x + w-module / 2, y-side-top + 0.4),
+      stroke: (paint: luma(120), thickness: 0.4pt, dash: "dash-dotted"),
+    )
+    line(
+      (m2-x + w-module / 2, y-side-bot - 0.4),
+      (m2-x + w-module / 2, y-side-top + 0.4),
+      stroke: (paint: luma(120), thickness: 0.4pt, dash: "dash-dotted"),
+    )
+    line(
+      (m3-x + w-module / 2, y-side-bot - 0.4),
+      (m3-x + w-module / 2, y-side-top + 0.4),
+      stroke: (paint: luma(120), thickness: 0.4pt, dash: "dash-dotted"),
+    )
+
+    // Dimension: Module Pitch (38.1 mm / 1.5")
+    line(
+      (m1-x + w-module / 2, y-side-top + 0.35),
+      (m2-x + w-module / 2, y-side-top + 0.35),
+      mark: (start: "stealth", end: "stealth"),
+      mark-size: 0.08,
+      stroke: 0.6pt + black,
+    )
+    content(((m1-x + m2-x + w-module) / 2, y-side-top + 0.55), text(
+      size: 6.5pt,
+    )[$qty(38.1, "mm")$ ($qty(1.5, "inch")$) pitch])
+
+    // =========================================================================
+    // VIEW C: CASSETTE RAIL GEOMETRY & RETENTION (ENLARGED DETAIL)
+    // =========================================================================
+    let x-rail-center = 4.8
+    let y-rail-center = -3.6
+    let rail-w = 38.1 * 0.08 // Magnified channel width (38.1 mm)
+    let rail-h = 6.35 * 0.08 // Magnified rail height (6.35 mm)
+    let lip-t = 1.2 * 0.08 // Sheet metal thickness (1.2 mm)
+
+    let rx1 = x-rail-center - rail-w / 2
+    let rx2 = x-rail-center + rail-w / 2
+    let ry1 = y-rail-center - rail-h / 2
+    let ry2 = y-rail-center + rail-h / 2
+
+    // View Title
+    content((x-rail-center, y-rail-center + 2.2), text(
+      size: 8.5pt,
+      weight: "bold",
+    )[VIEW C: CASSETTE RAIL GEOMETRY & RETENTION])
+    content((x-rail-center, y-rail-center + 1.85), text(
+      size: 7pt,
+      fill: luma(90),
+    )[(Cross-section of guide rail channel - scale enlarged)])
+
+    // Main Chassis Guide Channel (U-shaped metal guide track)
+    line(
+      (rx1 - 0.4, ry2 + 0.4),
+      (rx1 - 0.4, ry1 - lip-t),
+      (rx2 + 0.4, ry1 - lip-t),
+      (rx2 + 0.4, ry2 + 0.4),
+      stroke: 1.2pt + black,
+    )
+    line(
+      (rx1, ry2 + 0.4),
+      (rx1, ry1),
+      (rx2, ry1),
+      (rx2, ry2 + 0.4),
+      stroke: 1.2pt + black,
+    )
+
+    // Inserted Cassette Front Panel Lip (Mating into Channel)
+    rect(
+      (rx1 + 0.05, ry1 + 0.05),
+      (rx2 - 0.05, ry2),
+      fill: luma(230),
+      stroke: 0.8pt + black,
+    )
+
+    // Optional Spring Clip / Retention Latch (Contact spring on left side)
+    line(
+      (rx1 - 0.3, ry1 + 0.2),
+      (rx1 - 0.05, ry1 + 0.25),
+      (rx1 + 0.2, ry1 + 0.2),
+      stroke: 0.8pt + black,
+    )
+    circle((rx1 - 0.3, ry1 + 0.2), radius: 0.04, fill: black)
+
+    // Centerline
+    line(
+      (x-rail-center, ry1 - 0.6),
+      (x-rail-center, ry2 + 0.6),
+      stroke: (paint: luma(120), thickness: 0.4pt, dash: "dash-dotted"),
+    )
+
+    // Dimension: Channel Width (38.1 mm +0.2/-0.0 mm)
+    line((rx1, ry2 + 0.1), (rx1, ry2 + 0.7), stroke: 0.4pt + luma(140))
+    line((rx2, ry2 + 0.1), (rx2, ry2 + 0.7), stroke: 0.4pt + luma(140))
+    line(
+      (rx1, ry2 + 0.6),
+      (rx2, ry2 + 0.6),
+      mark: (start: "stealth", end: "stealth"),
+      mark-size: 0.08,
+      stroke: 0.6pt + black,
+    )
+    content((x-rail-center, ry2 + 0.85), text(
+      size: 7pt,
+    )[Channel width: $qty(38.1, "mm") +0.2/(-0.0)$])
+
+    // Dimension: Rail Height (6.35 mm / 0.25")
+    line((rx2 + 0.1, ry1), (rx2 + 0.7, ry1), stroke: 0.4pt + luma(140))
+    line((rx2 + 0.1, ry2), (rx2 + 0.7, ry2), stroke: 0.4pt + luma(140))
+    line(
+      (rx2 + 0.6, ry1),
+      (rx2 + 0.6, ry2),
+      mark: (start: "stealth", end: "stealth"),
+      mark-size: 0.08,
+      stroke: 0.6pt + black,
+    )
+    content(
+      (rx2 + 0.8, (ry1 + ry2) / 2),
+      text(
+        size: 6.5pt,
+      )[$qty(6.35, "mm")$ ($qty(0.25, "inch")$) rail height],
+      anchor: "west",
+    )
+
+    // Callout Annotations for View C
+    line(
+      (rx1 - 0.15, ry1 + 0.2),
+      (rx1 - 1.2, ry1 - 0.4),
+      stroke: 0.5pt + black,
+    )
+    content(
+      (rx1 - 1.25, ry1 - 0.4),
+      text(
+        size: 6pt,
+      )[Optional positive retention \ (spring clip / latch mechanism)],
+      anchor: "east",
+    )
+
+    line(
+      (rx2 - 0.3, ry1 + 0.1),
+      (rx2 + 1.2, ry1 - 0.4),
+      stroke: 0.5pt + black,
+    )
+    content(
+      (rx2 + 1.25, ry1 - 0.4),
+      text(
+        size: 6pt,
+      )[Metal-to-metal grounding contact \ (cassette lip insertion clearance)],
+      anchor: "west",
+    )
+  }),
+  caption: [Chassis dimensional requirements and module loading interface specifications detailing Side Elevation Cutaway (View A), Front Elevation Module Pitch Alignment (View B), and enlarged Cassette Rail Geometry & Retention Cross-Section (View C).],
+) <figure-chassis-dimensional-requirements-diagram>