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Control & signal cableMIL-DTL-24643/61 (LSPI)300 V Naval Shipboard ICLSZH XLPO -30 to +105 °C

LSPI MIL-DTL-24643 LSPI Low-Smoke Shipboard InteriorMIL-DTL-24643/61 300 V LSZH XLPO overall-braid-shielded multi-pair naval IC cable

Q: What does the U.S. Navy type designation LSPI stand for?

'LS' = Low-Smoke zero-halogen shipboard construction per MIL-DTL-24643, 'P' = Twisted Pairs, and 'I' = Interior communication and instrumentation cable with an overall braided copper shield. When supplied with an external braided aluminum armor over the jacket, it is designated LSPIA.

Q: How do the dash numbers M24643/61-01UN through -21UN map to conductor gauges?

In MIL-DTL-24643/61, dash numbers -01UN through -11UN (and their -01UA armored counterparts) cover 22 AWG (7×30) twisted pairs from 2 pairs up to 60 pairs, whereas dash numbers -12UN through -21UN cover heavier 18 AWG (7×26) twisted pairs from 2 pairs up to 50 pairs.

Q: Why did the U.S. Navy transition from older PVC/neoprene shipboard cables to MIL-DTL-24643 LSZH XLPO?

In enclosed below-deck shipboard compartments, burning PVC or polychloroprene releases dense black smoke that blinds firefighting crews and hydrochloric acid gas (HCl) that destroys combat-system electronics. MIL-DTL-24643 cross-linked polyolefin (XLPO) is halogen-free, low-smoke, and rated to +105 °C.

Q: When should I specify LSPI vs. individually pair-shielded MIL-DTL-24643 cables (such as LS2SJ or LSTTS)?

LSPI uses an overall braided tinned copper shield around all twisted pairs for compact diameter and lighter weight in general interior communications and alarm trunks. If individual circuits carry sensitive low-level analog audio or high-speed differential data requiring pair-to-pair isolation, specify an individually shielded MIL-DTL-24643 type.

LSPI (MIL-DTL-24643/61, M24643/61) 300 V low-smoke zero-halogen (LSZH) U.S. Navy shipboard IC cable with 2–60 twisted pairs of 22 or 18 AWG tinned copper, XLPO insulation, overall tinned copper braid shield, and LSZH XLPO jacket (-30 to +105 °C).

Approved

EMC screen

Low-EMC design

Flame-retardant

Configuration

Order designation: LSPI-7 (22 AWG)
Outer Ø ≈: 11.20 mm
Wall thickness: 1.23 mm
Total weight ≈: 190.0 kg/km
Min. bend R (fixed): 90 mm

All sizes (12)

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Engineering reply in 2 business hoursCut-to-length export drumsEN 10204 3.1 certificate per drum

Mil-Spec slash: M24643/61 (LSPI)
Rated voltage: 300 V RMS
Pair gauges: 22 or 18 AWG
Overall shield: Sn-Cu wire braid
LSZH materials: XLPO / XLPO
Temp. rating: -30…+105 °C

Typical values for this cable type, based on MIL-DTL-24643/61 (M24643/61) U.S. Navy Low-Smoke Shipboard Interior Comms — confirmed in the datasheet and quotation for your order.

Application fit

Is LSPI right for your machine?

Select MIL-DTL-24643/61 Type LSPI for naval surface combatant and auxiliary vessel interior communications (IC), sound-powered telephone trunks, bridge helm telemetry, and combat-system alarm distribution.

Quayside shore-to-ship HVSC connection

Suitable

XLPO insulation and LSZH jacket meet strict U.S. Navy MIL-DTL-24643 low-smoke, zero-halogen, and IEEE 1202 flame limits.

VFD inverter to AC motor screened feeder

Suitable

Balanced twisted pairs plus an overall tinned copper wire braid shield protect shipboard IC circuits against radar and propulsion EMI.

Immersion & wet locations

With conditions

Non-water-blocked for dry interior shipboard passages; for watertight bulkheads, use a water-blocked 'W' variant.

Energy chain / drag chain

Not suitable

7-strand tinned copper shipboard conductors are engineered for fixed naval cableway and hanger routing, not continuous drag chains.

Use JZ-50440 CP for drag-chain control

Typical machinesU.S. Navy & Allied Surface Vessel IC SystemsShipboard Bridge, Helm & Engine-Order TelegraphsCombat Information Center (CIC) Audio & AlarmsCoast Guard & Offshore Patrol Vessel CommsCommercial Marine & Subsea Support Vessel Control

Construction

Layer by layer

MIL-DTL-24643/61 (LSPI) construction: 7-strand tinned copper conductors (22 AWG or 18 AWG), colour/number-coded cross-linked polyolefin (XLPO) insulation twisted into pairs, binder tape, overall tinned copper wire braid shield, and black LSZH XLPO jacket.

Schematic, not to scale — generated from the layer data

#	Layer	Material & reference
1	7-strand tinned copper pairs	Concentric 7-strand tinned annealed copper wire per ASTM B33 (22 AWG = 0.35 mm² or 18 AWG = 0.82 mm²)Corrosion-resistant marine stranding compatible with standard naval terminal boards and MIL-DTL-38999 backshells
2	Cross-linked polyolefin (XLPO)	Irradiation or chemically cross-linked low-smoke zero-halogen polyolefin (105 °C rated, pair-identified)Thermoset core wall will not melt or drip during solder/heat-shrink termination or compartment fires
3	Halogen-free core binder tape	Low-smoke polyester/glass core wrap over the cabled twisted pairsMaintains round core geometry beneath the overall copper braid
4	Overall tinned copper braid shield	Braided tinned copper wire screen (36–34 AWG strands, ≥ 85 % optical coverage)Provides 360° EMI grounding into shipboard EMI stuffing tubes and connector backshells
5	Low-smoke XLPO outer jacket	Heavy-duty cross-linked polyolefin (LSZH XLPO, black) per MIL-DTL-24643Oil-, fuel-, and salt-fog-resistant naval jacket with ultra-low smoke and toxicity

LSPI-2 to LSPI-60 (22 AWG, M24643/61-01UN to -11UN)

22 AWG (7×30) 300 V multi-pair shielded shipboard interior communication cable (2 to 60 twisted pairs)

LSPI-2 to LSPI-50 (18 AWG, M24643/61-12UN to -21UN)

18 AWG (7×26) 300 V heavier-gauge shipboard IC and control twisted-pair cable (2 to 50 pairs)

Technical data

Ratings & operating limits

Typical values: Typical values for this cable type, based on MIL-DTL-24643/61 (M24643/61) U.S. Navy Low-Smoke Shipboard Interior Comms. Values for your order are confirmed in the datasheet and quotation.

Electrical

Rated voltage: 300 V RMS
Dielectric test voltage: 1,500 V AC RMS (core/core & core/shield)
Conductor DC resistance: ≤ 54.8 Ω/km (22 AWG) · ≤ 21.4 Ω/km (18 AWG) at +20 °C
Insulation resistance: ≥ 500 MΩ·km at +20 °C

Thermal

Continuous conductor temp.: -30 °C to +105 °C
Cold bend temperature: -30 °C without cracking

Mechanical

Pair construction: 2 to 60 twisted pairs (22 AWG or 18 AWG)
Overall shield: Braided tinned copper wire (≥ 85 % coverage)
Min. bending radius: 8 × overall cable diameter
Armoured option: Type LSPIA (braided aluminum armor over jacket)

Resistance

Flame propagation: IEEE 1202 / UL 1581 vertical tray flame test
Acid gas & halogen content: < 0.2 % halogen · acid gas < 5 mg/g
Smoke index & toxicity: Low optical smoke density & NES 713 compliant

Reference standards

Military specification: MIL-DTL-24643/61 (M24643/61)
RoHS & REACH: RoHS 3 & REACH compliant

Identification

Outer sheath colour: Black
Surface legend: M24643/61-[dash]UN LSPI-[size] TEBAOFLEX
Customs tariff (HS): 8544.49

Sizes

12 standard configurations (LSPI)

Engineering dimensions, conductor stranding, mass and electrical ratings for LSPI per MIL-DTL-24643/61 (M24643/61) U.S. Navy Low-Smoke Shipboard Interior Comms.

Dimensions & weights
Order designation	Cross-section / size	Conductor build	Wall ≈ mm	Outer Ø ≈ mm	Metal kg/km	Weight ≈ kg/km	Min. bend R fixed mm
Standard LSPI configurations
LSPI-2 (22 AWG)	2 PR × 22 AWG	M24643/61-01UN	1.10	7.90	39.2	89.0	63
LSPI-4 (22 AWG)	4 PR × 22 AWG	M24643/61-02UN	1.10	9.40	57.6	131.0	75
LSPI-7 (22 AWG)	7 PR × 22 AWG	M24643/61-03UN	1.23	11.20	83.6	190.0	90
LSPI-10 (22 AWG)	10 PR × 22 AWG	M24643/61-04UN	1.49	13.50	116.6	265.0	108
LSPI-15 (22 AWG)	15 PR × 22 AWG	M24643/61-05UN	1.71	15.50	156.2	355.0	124
LSPI-20 (22 AWG)	20 PR × 22 AWG	M24643/61-06UN	1.90	17.30	195.8	445.0	138
LSPI-30 (22 AWG)	30 PR × 22 AWG	M24643/61-08UN	2.27	20.60	279.4	635.0	165
LSPI-2 (18 AWG)	2 PR × 18 AWG	M24643/61-12UN	1.10	9.70	59.4	135.0	78
LSPI-4 (18 AWG)	4 PR × 18 AWG	M24643/61-13UN	1.29	11.70	90.2	205.0	94
LSPI-7 (18 AWG)	7 PR × 18 AWG	M24643/61-14UN	1.54	14.00	136.4	310.0	112
LSPI-10 (18 AWG)	10 PR × 18 AWG	M24643/61-15UN	1.87	17.00	189.2	430.0	136
LSPI-20 (18 AWG)	20 PR × 18 AWG	M24643/61-17UN	2.43	22.10	336.6	765.0	177

Typical values for this cable type; dimensions and weights for your order are confirmed in the quotation.
Outer diameters and weights are nominal engineering values for LSPI subject to standard manufacturing tolerances per MIL-DTL-24643/61 (M24643/61) U.S. Navy Low-Smoke Shipboard Interior Comms.

Electrical & rating data
Configuration	Max. DC R @ 20 °C Ω/km	Primary rating (A or nF/km)	Secondary rating	Dielectric test V AC rms
2 PR × 22 AWG	54.80	4.0	3.4	1,500
4 PR × 22 AWG	54.80	4.0	3.4	1,500
7 PR × 22 AWG	54.80	4.0	3.4	1,500
10 PR × 22 AWG	54.80	4.0	3.4	1,500
15 PR × 22 AWG	54.80	4.0	3.4	1,500
20 PR × 22 AWG	54.80	4.0	3.4	1,500
30 PR × 22 AWG	54.80	4.0	3.4	1,500
2 PR × 18 AWG	21.40	10.0	8.5	1,500
4 PR × 18 AWG	21.40	10.0	8.5	1,500
7 PR × 18 AWG	21.40	10.0	8.5	1,500
10 PR × 18 AWG	21.40	10.0	8.5	1,500
20 PR × 18 AWG	21.40	10.0	8.5	1,500

Electrical resistance at +20 °C and dielectric withstand voltages verified per MIL-DTL-24643/61 (M24643/61) U.S. Navy Low-Smoke Shipboard Interior Comms.

Quality & approvals

Testing & inspection

Routine tests on every production length, sample and type tests per batch — documented on an EN 10204 3.1 inspection certificate.

ConductorClass 5 stranding
Spark test100 % in-line
Lay-upCores, earth, fillers
SheathingInner, braid / screen, outer
Electrical testsAC voltage, resistance
DimensionsOD, wall thickness
Inspection documents & dispatchDrum & dispatch

Testing & inspection	Test value / reference	Frequency
Routine tests
Dielectric spark / high-voltage withstand test	100 % in-line spark and AC/DC dielectric withstand per MIL-DTL-24643/61 (M24643/61) U.S. Navy Low-Smoke Shipboard Interior Comms	Every manufactured length
Conductor DC resistance & continuity check	Within maximum 20 °C resistance limit specified for LSPI	Every spool or drum length
Sample tests
Insulation resistance & dimensional verification	Wall thickness, concentricity and insulation resistance per MIL-DTL-24643/61 (M24643/61) U.S. Navy Low-Smoke Shipboard Interior Comms	Per production batch
Environmental, mechanical & EMC qualification	Qualified to MIL-DTL-24643/61 (M24643/61) U.S. Navy Low-Smoke Shipboard Interior Comms thermal, mechanical and environmental performance criteria	Type qualification

Inspection certificate

Issued with every drum, listing the routine test results for that length.

Product approvals

MIL-DTL-24643/61 (M24643/61) U.S. Navy Low-Smoke Shipboard Interior CommsCE (2014/35/EU) & RoHS 3 (2015/863/EU) CompliantREACH SVHC Compliance Verified

Company certificates

ISO 9001ISO 14001ISO 45001VDE marks approvalUL / cULCE · LVD / EMC

Marking & supply

Ordering & delivery

Sheath marking

M24643/61-03UN LSPI-7 (22 AWG) 300V LOW SMOKE SHIPBOARD TEBAOFLEX

Delivery form: Export wooden drums, tactical reels or coils
Standard lengths: 100 m · 500 m · 1000 m (or custom cut lengths)
MOQ: 100 m (stock sizes) · 300–500 m (custom build)
Lead time: 2–4 weeks ex-works
Incoterms: EXW, FOB, CIF, DAP

Technical documents

Downloads

PDFLSPI MIL-DTL-24643 LSPI Low-Smoke Shipboard Interior – technical datasheet12 sizes · construction, technical data, approvals XLSXLSPI spec data (Excel)All 12 sizes with dimensions and data, for your BOM or quotation

Revision: 2026-10-20
Updated: 2026-10-20

FAQ

Questions engineers ask first

Not covered here? Send your drawing — an engineer replies within 2 business hours.

What does the U.S. Navy type designation LSPI stand for?

'LS' = Low-Smoke zero-halogen shipboard construction per MIL-DTL-24643, 'P' = Twisted Pairs, and 'I' = Interior communication and instrumentation cable with an overall braided copper shield. When supplied with an external braided aluminum armor over the jacket, it is designated LSPIA.

How do the dash numbers M24643/61-01UN through -21UN map to conductor gauges?

In MIL-DTL-24643/61, dash numbers -01UN through -11UN (and their -01UA armored counterparts) cover 22 AWG (7×30) twisted pairs from 2 pairs up to 60 pairs, whereas dash numbers -12UN through -21UN cover heavier 18 AWG (7×26) twisted pairs from 2 pairs up to 50 pairs.

Why did the U.S. Navy transition from older PVC/neoprene shipboard cables to MIL-DTL-24643 LSZH XLPO?

In enclosed below-deck shipboard compartments, burning PVC or polychloroprene releases dense black smoke that blinds firefighting crews and hydrochloric acid gas (HCl) that destroys combat-system electronics. MIL-DTL-24643 cross-linked polyolefin (XLPO) is halogen-free, low-smoke, and rated to +105 °C.

When should I specify LSPI vs. individually pair-shielded MIL-DTL-24643 cables (such as LS2SJ or LSTTS)?

LSPI uses an overall braided tinned copper shield around all twisted pairs for compact diameter and lighter weight in general interior communications and alarm trunks. If individual circuits carry sensitive low-level analog audio or high-speed differential data requiring pair-to-pair isolation, specify an individually shielded MIL-DTL-24643 type.

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LSPI MIL-DTL-24643 LSPI Low-Smoke Shipboard Interior

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