Repeated-Input Console Drift Maps a Shared Interface Fault

Last updated: August 4, 2026

⚠️ Scope and Disclaimer: This article is written for clinical engineering managers and equipment procurement decision-makers evaluating interface-layer component replacement for ultrasound consoles. It does not constitute repair instructions. Installation should be performed by qualified biomedical engineers following the OEM service manual and electrical safety protocols. Pricing ranges cited are industry estimates and vary by region, supplier, and unit condition. Samsung Medison is a trademark of Samsung Electronics Co., Ltd.; geprobe is an independent third-party supplier and is not affiliated with or endorsed by Samsung.

The first four articles in this series traced a full degradation timeline—from panel main board navigation decay to keyboard assembly cluster drift, from clustered hesitation to session-length drift. Every one of them started from the same place: symptoms visible enough that someone—an operator, a tech—flagged that something was wrong.

This article is about an earlier stage. Early enough that the operator hasn't formed a clear impression. Early enough that the drift only appears under one specific condition: after repeated inputs.

Morning cold boot, first patient—everything is normal. Six patients into the morning, one key cluster starts to feel slightly less crisp. Lunch break—the machine stays on but sits idle for an hour—and things seem better again. By the fifteenth patient of the afternoon, menu transitions are hesitating, one function-key group needs a second press to respond. Shut down for the night. Tomorrow morning, cold boot—normal again.

This stage is called repeated-input drift. It is not driven by heat accumulation—if it were, sitting idle for an hour (with the enclosure still warm) wouldn't improve anything. The trigger is every single keystroke, every signal transition, wearing down the shared interface layer at the nanometer scale. Repeated interaction is the degradation mechanism. This article explains how to recognize that stage, how to use drift patterns to map the shared interface fault in reverse, and why the procurement decisions you make during this window are sharper than at any later point on the timeline.

What follows covers the full decision chain:

Section 1: Why "drifts after repeated inputs" and "drifts after running for hours" are two different degradation curves—and why telling them apart changes what you buy
Section 2: The physics of the shared interface layer—how every signal transition consumes the contact surface at the nanometer scale
Section 3: Mapping the interface fault in reverse—a three-step diagnostic that converts drift patterns into a component-level bill of materials
Section 4: Samsung Medison shared interface layer procurement—a three-tier architecture, a symptom-to-component decision tree, and a category overview
Section 5: Samsung interface component procurement checklist—five pre-order questions tailored to interface-layer parts and acceptance testing built around the repeated-interaction stress test

Repeated-Input Drift Is Not Session-Length Drift — Same Console, Two Different Degradation Curves

Session-length drift, as the fourth article in this series detailed, is heat-accumulation-driven: component temperature rises with runtime, ESR climbs, contact resistance increases, clock jitter worsens—symptoms appear after three hours of operation, disappear after a full cool-down. Its core variable is time.

Repeated-input drift has a different core variable: count. Not "how long has it been on," but "how many times has it been used." The difference isn't academic. It directly determines which component you buy.

Heat Accumulation vs. Signal-Transition Fatigue: Why "Drifts After 30 Presses" Is a Sharper Diagnostic Than "Drifts After 3 Hours"

Imagine two identical Samsung ultrasound consoles. Both show sluggish menu response in the afternoon.

Console A: Normal all morning. By 2 PM, menu switching slows, the trackball feels loose. Power down for an hour to cool—normal for 20 minutes after reboot, then drift resumes. This is the heat accumulation pattern. The fault sits somewhere on a temperature-affected shared path, distributed across three possible tiers: Control Panel Board, Key Matrix Controller, or Interface Board.

Console B: Normal for the first 30 minutes after cold boot. But you notice something—the sonographer doing abdominal exams (heavy measurement-key usage) starts needing second presses on the measurement cluster by the third abdominal study. The vascular sonographer (using a different key group) has no complaints. More telling: at lunch, the machine stays on but sits idle for an hour. The measurement-key drift improves—not gone, but noticeably less frequent. Afternoon workload picks up, heavy measurement-key use resumes, and the drift returns. This is the repeated-interaction pattern. The fault sits at one specific physical node that every keystroke wears down—not the whole shared path, but the particular connection point that every press crosses.

💡 Expert Insight: Heat-accumulation drift tells you "the fault is somewhere on this path." Repeated-input drift tells you "the fault is at this node on this path." The diagnostic resolution is an order of magnitude higher. On a Samsung Medison platform—where the interface layer is split into multiple independently replaceable components—diagnostic precision directly translates to whether you spend $80 on a ribbon cable or $800 on a complete UI module. The 15-minute stress test in Section 3 is the difference between those two numbers.

A Single Console Can Run Both Curves Simultaneously—You Need to Separate Them

A Samsung ultrasound console with four years of service can absolutely run heat-accumulation and repeated-interaction degradation at the same time. Connector fretting corrosion (nanometer-scale oxidation wear at the contact surface, detailed in Section 2) is driven by keystroke count. Capacitor ESR creep is driven by temperature and age. When both mechanisms overlap, the operator's experience is: "By the thirtieth patient this afternoon, I was done tolerating it."

The way to separate them: the idle test. After three hours of heavy use, don't power down. Have the operator walk away from the console for 30 minutes—no keystrokes, but the machine stays on, enclosure temperature unchanged. Then run another round.

Drift clearly improves after the idle period → repeated-interaction is the primary driver (no new wear during idle, but temperature didn't drop—heat accumulation can't explain the improvement)
Drift is unchanged or worse after the idle period → heat accumulation is the primary driver (temperature persisted, idle changed nothing)
Drift improves partially but not completely → both mechanisms are running—the heat-accumulation component stayed, the repeated-interaction component temporarily subsided

What Repeated-Input Drift Gives You That Later Stages Don't

Advantage	What It Means in Practice
Actively reproducible	You don't need to wait for a long session to unfold naturally—15 minutes of high-frequency key pressing on a cold machine can trigger the pattern via cumulative interaction stress
Precisely localizable	Drift follows functional key groups, not the whole keyboard evenly—directly pointing to which specific node in the interface layer is degrading
Long diagnostic window	From the onset of repeated-input drift to the onset of session-length drift, you typically have 3–6 months of quiet procurement runway
Low verification cost	After replacing the target component, a 15-minute stress test confirms whether the fix worked—no need to wait an entire day

The Physics of the Shared Interface Layer — Every Signal Transition Consumes the Contact Surface

To understand why repeated inputs trigger drift—and why drift always arrives in groups rather than single keys—you need to look one layer down: the physical interface layer, the place where an operator's keystroke becomes a digital signal the system can read. On Samsung Medison architectures, this layer includes connector gold fingers, ribbon cables, buffer ICs, and interface board PCB traces. Four components. One shared fate: every signal transition consumes a small amount of their physical integrity.

Connector Fretting Corrosion — Nanometer-Scale Wear on Gold Fingers

Gold-finger connectors don't rely on solder. They rely on mechanical spring pressure to maintain contact. This design enables modular replacement, but it carries a cost: the contact surfaces undergo nanometer-scale reciprocating wear under micron-level vibration.

Every keystroke sends a small mechanical impulse through the keycap, through the silicone membrane, into the PCB—and from the PCB into every connector on the board. The gold finger and its socket spring slide against each other by perhaps 0.1–0.5 microns. A single displacement is irrelevant. But a console handling 30 patients per day, each exam averaging 200 keystrokes, accumulates 6,000 key-press impulses per day—roughly 2.2 million per year. Over three years: 6.6 million micro-friction events.

Each micro-slide scrapes away an atomically thin layer of oxide, exposing fresh metal—which then re-oxidizes. Scrape, oxidize, scrape, oxidize. After millions of cycles, the effective contact area drops from near 100% at manufacture to perhaps 60–70%. Contact resistance drifts from 20–50 mΩ to 200–500 mΩ.

The I²C bus rise time τ = R × C. R increases by a factor of 10, the rise edge stretches by a factor of 10. It exceeds the receiving chip's setup-time window. The data packet fails checksum verification. The keystroke event is silently discarded. What the operator feels: "Pressed it. Nothing. Pressed it again—there it is." On the second press, the micro-displacement happened to land on a patch of contact surface that was still clean, resistance temporarily dropped, the signal got through. The operator assumes they pressed too lightly the first time. They didn't. The connector surface, at nanometer scale, is no longer intact.

Ribbon Cable Copper Foil Micro-Cracks — How Keystroke Vibration Reaches the Interface Layer

The ribbon cable (Flexible Flat Cable) connects the keyboard module to the interface board. It looks stationary. It isn't. Every keystroke produces a tiny PCB flexure that transmits through the mounting points to the ribbon cable root—the point of tightest bend radius—where the copper traces undergo repeated tension-compression cycles.

Fresh ribbon cable: uniform copper grain structure, consistent impedance across all traces. After 10,000 flex cycles: micro-cracks begin to nucleate at grain boundaries in the thinnest sections of copper foil. After 100,000 cycles: micro-cracks connect into localized high-impedance zones. High-frequency signals—the dense pulse trains generated by rapid successive keystrokes—experience measurably greater attenuation through these zones than low-frequency signals. What the operator feels: "Typing at normal speed is fine. But when I move through the menu fast, the third or fourth press doesn't take." That third pulse arrives while the localized heat from the first two pulses hasn't dissipated at the high-impedance zone—instantaneous impedance is even higher, and the signal collapses below the detection threshold.

⚠️ Watch Out for the Reseat Illusion: Unplugging and re-seating the ribbon cable temporarily improves symptoms. This is a known misleading signal. The act of unplugging scrapes away some of the oxide layer on the connector contact surfaces, temporarily lowering contact resistance—but it does nothing for copper foil micro-cracks. Symptoms return within a week. If "reseat the ribbon and it's fine" has happened twice or more on your machine, the cable itself needs replacement, not another reseat.

Buffer IC Drive Strength Degradation — Why High-Frequency Key Zones Fail First

The buffer chip on the interface board (e.g., a 74LVC245 octal bus buffer or equivalent—Samsung platforms may use different part numbers across product generations) has one job: take the weak signal from the keyboard matrix and amplify it to a level the system bus can reliably read.

This chip is active for essentially the entire life of the console—any time the machine is powered on, it's driving the bus. After hundreds of millions of switching cycles, trap charges accumulate in the gate oxide of the output-stage PMOS and NMOS transistors. Threshold voltages drift. Drive current declines from the factory-spec 24 mA toward 12–16 mA.

When drive strength drops, signal rise times slow. Under light load—the system is idle, one key is pressed occasionally—the weakened buffer still manages. Under heavy load—the operator is switching rapidly through measurement menus, using multi-key combinations, rolling the trackball, bus capacitance at maximum—the buffer's output waveform collapses. Signal integrity margin (the voltage and timing headroom between what the receiving chip gets and what it needs to reliably detect a logic level) drops to zero.

This is why high-frequency key zones drift first. Not because those keys are mechanically failing. Because they happen to share the output channel of a buffer chip whose drive strength has degraded to the point where it cannot maintain signal quality under full load. Low-frequency zones—system setup keys, archive keys, print keys—remain normal. The buffer only fails when it's being asked to work hard.

Why Drift Always Arrives in Groups—and Why That's Actually Useful

Single-key drift (one fixed key occasionally needs a second press, no other key affected) → keycap mechanical fault or localized silicone membrane damage. Not an interface-layer problem.

Grouped drift (a functionally related set of keys—say, all measurement-function keys, all menu-navigation keys—drift together under the same conditions) → shared interface layer problem. Those keys share a connector channel, a ribbon cable trace group, or a buffer IC output bank.

Grouped drift is not more alarming than single-key drift. It is more informative. If the measurement key cluster drifts but the alphanumeric keys don't—you already know which buffer channel is degrading, or which ribbon trace group has micro-cracks. No disassembly. No oscilloscope. A control panel layout diagram and a marker pen.

Map the Interface Fault in Reverse — A Three-Step Diagnostic

Diagnosing repeated-input drift doesn't require expensive tools. It requires a warm machine, an operator willing to spend 15 minutes on a structured test, and a piece of paper.

Step 1: Draw a High-Frequency / Low-Frequency Usage Heat Map

Print a control panel layout diagram (grab one from the OEM service manual). Ask the operator—or better, ask two or three operators who regularly use this specific machine—to label each key zone by average daily usage frequency:

🟢 Low-frequency zone (< 50 presses per day): system setup keys, print keys, archive keys, patient info edit keys
🟡 Mid-frequency zone (50–200 presses per day): soft keys, mode-switch keys, body-marker keys
🔴 High-frequency zone (> 200 presses per day): measurement function keys (distance, area, volume), menu navigation keys, freeze/unfreeze, trackball, enter key

Operators don't need exact numbers. They look at the layout and know immediately "I use this row constantly" or "I barely touch this area." Have two or three operators label independently, then take the intersection—the overlap is the objective pattern; the differences are individual workflow habits.

Step 2: 50-Press Consecutive Stress Test × 2 Rounds

Select every 🔴 high-frequency zone from the heat map, plus at least one 🟢 low-frequency zone as a control.

Round 1: Within 30 minutes of cold boot. For each selected zone, have the operator press the same key (or rotate through keys in that zone) 50 consecutive times, rapidly. Record the number of "needed a second press to register" events per zone—the drift count.

Round 2: After 3+ hours of continuous operation. Same operator, same zones, same 50-consecutive-press protocol. Record drift counts again.

Interpreting the gap:

Low-frequency zone: near-zero drift in both rounds. High-frequency zone: Round 2 drift count significantly higher than Round 1 → Repeated-input drift confirmed. Fault is in the shared interface layer. The interface component degrades under cumulative keystroke stress.
Low-frequency and high-frequency zones both measurably worse in Round 2, and a 30-minute idle period (no keystrokes, machine on) does NOT improve them → Heat-accumulation drift. Fault is at the input-path board level—refer to Part 4 of this series.
Low-frequency and high-frequency zones both show similar drift counts in both rounds, and drift is limited to one fixed key → Single-key mechanical fault. Not an interface-layer issue.

Step 3: Map the Drift Cluster Pattern to the Interface Tier

Drift Coverage Pattern	Interface-Layer Target	Samsung Model Reference	Procurement Priority
Whole keyboard drifts uniformly (alphanumeric + function + numeric keys all affected; touchscreen normal)	Signal path between keyboard interface board and main board	BD-337-KI Keyboard Interface Board	First priority—replace board; symptoms should resolve completely
Only specific function-key zones drift (e.g., measurement-key cluster drifts, alphanumeric keys normal, touchscreen normal)	Micro-cracks in the ribbon cable trace group for that key zone, or oxidation on the specific connector pins serving those keys	H339-SIG-02 Keyboard Cable	First priority—replace cable first (lower cost); escalate to interface board only if symptoms persist
Physical keyboard + touchscreen + trackball all drift together (entire control surface affected)	Complete UI module or PC interface board	Complete User Interface / Control Panel / PCB-363-PI-00-00 PC Interface	Confirm cable and interface board replacement don't resolve before escalating to full UI
Only touchscreen drifts (physical keyboard normal, touch targets require repeated taps)	USB touch interface board	BD-346-TOUCH-USB Board	Independent touch signal path—does not run through keyboard interface board or keyboard cable

💡 Expert Insight: Samsung Medison's split interface architecture creates real cost differentials here. Whole-keyboard drift → BD-337-KI interface board ($100–350). Ribbon-only drift → H339-SIG-02 cable ($30–80). Full-UI drift → Complete User Interface ($400–1,200). Diagnostic precision directly converts to procurement budget precision. Spending an extra 15 minutes on the heat map and stress test can save $300–800 in unnecessary component replacement. On a GE platform, you'd replace the entire Control Panel Board for any of these patterns—the diagnostic effort is lower, but the part cost is higher. On Samsung, the cost savings are there, but they're gated behind accurate pre-purchase localization.

Samsung Medison Shared Interface Layer Procurement — A Three-Tier Architecture

Samsung Medison's interface-layer architecture is fundamentally different from GE's. GE integrates key scanning, encoder interface, LCD drive, and backplane communication onto a single Control Panel Board (e.g., 5207000-28)—any keyboard drift → replace the whole board. The diagnosis is simpler. The component cost is higher. Samsung splits the interface layer into independently replaceable components—diagnosis must be more precise, but replacement cost is lower and more targeted.

Samsung Interface Layer: Three Tiers

Tier	Component Type	Samsung Representative Model	Functional Scope	Typical Repeated-Input Drift Presentation
L1: Signal Cable	Keyboard signal ribbon cable	H339-SIG-02 Keyboard Cable	Physical signal transport from keyboard module to interface board	Specific function-key zone drift, not whole keyboard; symptoms temporarily improve after ribbon reseat (false signal—copper micro-cracks remain)
L2: Interface Board	Keyboard interface board / PC interface board	BD-337-KI Board / PCB-363-PI-00-00 PC Interface	Signal buffering + level translation + connector adaptation	Whole keyboard drifts uniformly, touchscreen normal; high-frequency zones expose first, low-frequency zones follow
L3: Complete UI Module	Full user interface / control panel assembly	Complete User Interface / Control Panel	Physical keyboard + interface board + touchscreen + trackball + housing—plug-and-play	Physical keyboard + touchscreen + trackball all drift together; or L1/L2 replaced and symptoms persist

Symptom → Component Decision Tree

Which input devices are drifting?

├── Physical keyboard only; touchscreen and trackball are normal
│   ├── Whole keyboard drifts uniformly (alphanumeric + function + numeric keys)
│   │   → BD-337-KI Keyboard Interface Board ($100–350)
│   │      If drift partially remains after board swap → cable is a co-factor; add H339-SIG-02
│   │
│   └── Only specific function-key zones drift (e.g., measurement cluster, menu-nav keys)
│       → H339-SIG-02 Keyboard Cable ($30–80)
│          Symptoms resolve after cable replacement = confirmed. Symptoms persist → cable is not the cause; escalate to interface board
│
├── Physical keyboard + touchscreen + trackball all drift together
│   ├── Normal cold, drift after repeated interaction across the entire UI
│   │   → PCB-363-PI-00-00 PC Interface ($100–300)
│   │      PC Interface Board is the shared upstream channel for keyboard + touch + trackball
│   │
│   └── Drift present even cold, OR L1/L2 replacements didn't resolve
│       → Complete User Interface / Control Panel ($400–1,200)
│
└── Only touchscreen drifts; physical keyboard is normal
    → BD-346-TOUCH-USB Board (touch USB interface board)
       Touchscreen runs on an independent signal path—does not pass through keyboard interface board or keyboard cable

geprobe Samsung Interface / UI Category Overview

The geprobe parts catalog covers 327 Samsung Medison products. The shared-interface-layer subset relevant to this article:

Category	Product Count	Representative Models
Interface Boards (Interface / KI Board / PC Interface)	8+	BD-337-KI, PCB-363-PI-00-00, BD-337-KMM0A, BD-337-RR Rear Panel Right
Signal Cables (Keyboard Cable / Flat Cable / Signal Cable)	5+	H339-SIG-02, Flat Cable
Complete UI (User Interface / Control Panel)	5+	Complete User Interface, Control Panel, User Interface
Touch Interface (Touch USB / Touch Screen)	5+	BD-346-TOUCH-USB, Touch Screen, B22514209902928 Touch Screen

Samsung Interface Component Procurement Checklist — and the Repeated-Interaction Stress Test That Validates the Fix

Five Questions to Ask Before Ordering (Interface-Layer Edition)

Samsung Medison's product lines (RS80A / RS85 / HS40 / HS50 / H60 / WS80A and others) have undergone significant interface specification changes across generations. Interface-layer components are even more sensitive to compatibility mismatches than board-level components—a ribbon cable with the wrong pin count won't plug in; a buffer chip with the wrong suffix may have incompatible drive strength. These five questions are not boilerplate:

#	Question	Why It Matters More for Samsung Interface Components
1	Is the connector type and ribbon pin count on this component compatible with my specific system? (Attach system serial number and firmware revision.)	Samsung may have shipped different connector pitches and pin counts within the same product line (e.g., RS80A) across production years. Physically won't plug in = dead on arrival
2	If this is an interface board (BD-337-KI or PCB-363-PI), is the buffer IC part number identical to or compatible with the one on my original board?	A buffer chip with a different suffix may have different drive strength (24 mA vs. 12 mA). Symptoms may appear to improve while margin remains critically thin—recurrence in 6 months
3	Is the ribbon cable sold separately or bundled with the interface board? If separate, what are the pin count, pitch, and same-side/opposite-side contact specifications?	Samsung ribbon cables aren't always quoted as standalone items—many suppliers bundle them with the interface board. If you only need the cable, confirm the supplier will split the bundle
4	Is the component new or a tested pull from a decommissioned unit? If a pull, what is the condition of the contact surface plating and the estimated remaining flex-life on the ribbon cable?	Interface-layer components (cables, connectors) degrade by usage count, not just age. A pulled ribbon cable may have already accumulated a meaningful fraction of its flex-fatigue life—the supplier should disclose test scope and remaining-life estimate
5	Does the quoted price include shipping and estimated transit time? Which warehouse does it ship from? If drift symptoms persist after installation, what is the return/exchange policy? (Interface-layer diagnosis can involve tier iteration—you bought an interface board but the root cause was the cable. Can you exchange?)	Samsung's split interface architecture means you may need two-tier investigation. Exchange flexibility directly determines your total procurement cost

Post-Installation Acceptance Testing — Centerpiece: The Repeated-Interaction Stress Test

A standard full-key traversal (press every key once → confirm response) will not catch interface-layer problems. Signal margin under light load may still be sufficient. Interface-layer component acceptance must use stress conditions: high frequency, consecutive, full load.

#	Test	Duration	Pass Criterion
1	Full key traversal	5 min	Every key registers correctly on the first press
2	Cold-machine 50-press stress test	Within 30 min of boot	Every high-frequency zone: 50 consecutive rapid presses—zero drift (every single press registers on the first attempt)
3	Warm-machine 50-press stress test (non-negotiable)	After 3+ hours of operation	Same high-frequency zones, same 50-consecutive-press protocol—drift count must be statistically indistinguishable from the cold-machine round. If the warm round drift count exceeds the cold round → another interface-layer component is still degrading under thermal load; you may have replaced the wrong tier
4	Full-load multi-key combination test	3 min	Function-key combinations, Shift + function keys, rapid menu cycling—all normal, no latency, no dropped events
5	Electrical safety verification	5 min	Leakage current < 100 µA (normal) / < 500 µA (single-fault)

⚠️ Watch Out: The most common omission in interface-layer acceptance testing is the warm-machine stress test. Interface-layer components—particularly buffer ICs and connectors—degrade more severely warm than cold. A cold pass does not guarantee a warm pass. If the supplier says "we pressed every key once and it worked," that is not sufficient. Require at least 3 hours of thermal stabilization followed by a second round of 50-press stress testing. If the supplier can't or won't perform this test before shipping, run it yourself before signing off on the installation.

Key Takeaways: Repeated-Input Drift Is the Most Underrated Procurement Signal on the Degradation Timeline

Repeated-input drift produces the cleanest diagnostic signal on the entire degradation timeline. It appears only after you've used the console repeatedly—not driven by hours of runtime and heat accumulation, but by the cumulative effect of every signal transition consuming the contact surface at nanometer scale. It improves after an idle period—not because the machine cooled down, but because wear paused. This unique signature lets you actively reproduce the problem in 15 minutes of structured testing, localize it to a specific interface tier, and buy only the layer that actually failed.

Samsung Medison's split interface architecture is a double-edged sword. The upside: you can replace only the failed tier—ribbon cable $30–80, interface board $100–350, complete UI $400–1,200—rather than swapping an entire integrated Control Panel Board as the GE platform requires. The downside: the diagnosis has to be right. Replace the interface board when the real fault is ribbon micro-cracks → symptoms persist → buy the cable too. Three-tier iteration can cost more than starting with the complete UI. But if you follow the three-step diagnostic in this article—heat map → stress test → cluster-to-tier mapping—the risk of tier iteration drops to near zero.

The most expensive choice, across every brand and architecture, is always "wait." Wait until repeated-input drift escalates to session-length drift (Part 4), then to clustered hesitation (Part 3), then to cluster drift (Part 2), then to hard failure (Part 1). The same component costs more to acquire at each successive stage—not because the part's price tag changes, but because your negotiating leverage, shipping options, and downtime control erode at every step.

For Samsung Medison platform users, the standard procurement path for the BD-337-KI Keyboard Interface Board, H339-SIG-02 Keyboard Cable, PCB-363-PI-00-00 PC Interface, and Complete User Interface is: submit your system serial number → receive a quote within 6 hours → standard logistics, 3–7 days → run the cold + warm stress test per the acceptance protocol in this article → done. During the repeated-input drift window, that path is wide unhurried, and you have options. During the hard-failure stage, that same path compresses to "express freight + whoever has stock + the machine goes down today." Same component. Different timing. Different total cost.

Series articles:

Why A Console That Only Starts Drifting After Repeated Inputs May Already Be Mapping a Shared Interface Fault