German Parachute Mines

[Chris Goss]

I hope that someone can solve a series of puzzles. I am researching KGr 126 and the mines it dropped in 1940 and documents make mentions of these mines usually as follows:

LMBIII Gruen VH92

To me this is LM type B development III. However, what is VH 92 (and for that matter VH46, VH48, VH24, VH14)?

Other colours are Blau, Gelb, Rot, Weiss.

Also ZK4 and ZK6 are mentioned. ZK = Zählkontakt which is counting contact where the mine becomes live only after a specified number of ignition contacts (1-15 ships have gone over the mine).

Suggestions welcome!

[Snautzer]

Fusing of mine

Technical Summary: German VH-Series Fuze Amplifiers (LMB III)
The Verstärker-Haube (VH) units served as the electronic "brain" for German magnetic influence mines. Their primary function was to amplify the minute electrical changes detected by magnetic sensors (like the A-Unit needle or induction coils) to trigger the mine's detonator.
Type Era Primary Function & Technical Focus
VH 14 1939-41 Early Standard: Single-tube amplification for static magnetic deviation. Highly sensitive to early Allied magnetic sweeps.
VH 24 1940-42 Stability Upgrade: Introduced a 24-minute mechanical/electronic arming delay to allow the magnetic needle to settle post-impact.
VH 46 1942-44 Coastal Specialist: Optimized for shallow water with high vertical field sensitivity and early anti-pulse filtering.
VH 48 1943-45 Induction Logic: Detected the rate of change in magnetic fields. Designed to defeat degaussed ships and fast-moving sweepers.
VH 92 1944-45 Late-War Peak: Most advanced filters; often integrated with acoustic/pressure sensors for multi-influence detonation.
Core Technical Architecture
Circuitry: Vacuum-tube based (primarily RV2,4P700 tubes) to provide high gain with low power consumption.
Power Supply: Dual-voltage dry batteries (typically 4.5V for filaments and 90V for the anode circuit).
Safeties: Hydrostatic switches ensured the VH unit remained inert until reaching a specific depth.
Counter-Countermeasures: Late models included "Vessel Counters" and anti-recovery tilt switches as detailed in the Cat-UXO database.
Historical Context
The evolution from VH 14 to VH 92 reflects the technological race against Allied degaussing (magnetic signature reduction). As ships became "quieter," VH units became more sensitive and capable of filtering out artificial sweeping pulses

[Chris Goss]

I suspected as much so thanks very much for this. What about the colours?

[Snautzer]

For the German LMB III (Luftmine B) sea mine, colors were used as a critical functional code for ground crews and ordnance experts to identify the mine's sensors and safety risks:
Firing Unit Identifiers
Yellow (Gelb): Marked mines with Magnetic sensors (e.g., M1, M2). These triggered when a ship's steel hull disrupted the Earth's magnetic field.
Blue (Blau): Marked mines with Acoustic sensors (e.g., A1, A2). These were hydrophones that detected the specific sound frequencies of ship propellers.
Green (Grün): Marked mines with Pressure sensors (e.g., D1, D2). These detected the dip in water pressure caused by a ship passing overhead.
Combinations: It was common to see mixed markings (e.g., Yellow + Green) indicating a "combined influence" mine that required both signatures to detonate.
Safety & Operational Markings
Red (Rot): A danger warning indicating Anti-handling devices (Zusatz-Zünder). These were booby-traps designed to detonate the mine if it was moved, opened, or lifted by Allied disposal teams.
White (Weiss): Used for technical stenciling. This included the serial number, weight (e.g., ~1000 kg), filling date, and explosive type (usually S3 or Hexanite).
Visual Appearance
Body Color: The main casing was typically painted in RLM 02 Grey or RLM 70/71 Dark Green for maritime camouflage.
Parachute: The parachute used to drop the mine was often Green or Red to aid in camouflage or recovery identification.

[Chris Goss]

Thanks!

[edwest2]

Thank you Snautzer.