From the 1968 Shure Brothers Microphone Catalog:
CONTROLLED MAGNETIC “404” SERIES
… THE STANDARD OF THE INDUSTRY
Without a doubt, the strongest and most practical close-talking micro phone for ANY mobile application. It is the most widely used mobile microphone among police, taxicab and fleet truck operators. Exclu sive ARMO-DUR Tlii case is comfortable to hold in hot or cold weather … is immune to oil, grease, fumes, sun, salt, spray, rust and corrosion … outstanding in its ability to withstand mechanical shocks and vibration. The rugged war-time proved, Shure-patented Controlled Magnetic cartridge has specially tailored response for high speech intelligibility. Lightweight … easy to use … fits snugly in the palm of the hand. “Million-cycle” leaf-type switch controls the microphone circuit and an external relay or switching circuit. Fully shielded against electric and magnetic fields. Only 3″ high, 2″ wide, 1″ deep. Includes built-in “lifetime” hang-up button and mounting bracket. Semi-directional.
Model 405T (only) has a built-in transistorized amplifier for improve ment-replacement of most carbon microphones. Does not require bat teries or extra power supplies. Provides greater clarity, and freedom from aging (common to carbon microphones)
A DOZEN GOOD REASONS WHY THE 404 SERIES IS YOUR BEST BUY IN MOBILE COMMUNICATIONS MICROPHONES
- World Famous “Controlled Magnetic Cartridge”- Field-proved throughout the world under extreme conditions of military and com mercial use.
- Corrosion Proof “Armo-Dur” Housing-Immune to severe weather conditions. Unaffected by corrosive materials normally encountered or used: oils, grease, fumes, salt spray, etc.
- High Impact “Armo-Dur” Housing- Has high elasticity limits. Resists extreme mechanical shocks and retains original shape.
- Constant Impact Strength-Withstands mechanical shocks under varying conditions of temperature- with uniform impact resistance. (Varies only 25% in impact strength through a range running from -40° to 165° fahrenheit-as compared to a variance of 95% for standard die-cast housings.)
- Eliminates Shock Hazard- Special “Armo-Dur” housing is an insulator- eliminates electrical shock hazard.
- Reduces Operator Fatigue– Under actual operating conditions, the complete microphone (including plug and cable) weighs only 8 oz., 42.9% less than similar die-cast microphones. The net weight of the microphone, plug, and cable is 12 oz., 33.3% less than similar die-cast microphones.
- No Vibration Fatigue- “Armo-Dur” eliminates shattering, break ing or cracking of housing often caused by continuous vibrations.
- Color Permanence- Color runs throughout the “Armo-Dur” housing. It is unafFected by handling, sun and corrosive fumes or materials which are normally encountered or used.
- Low Thermal Conductivity-Feels normal to the hand in extreme heat or cold.
- “Life-Time” Hang-Up Button-Unique shock mounting prevents button “pull out”.
- Fully Shielded- A high permeability shield and the vacuum metalizing on “Armo-Dur” case provide effective shielding against electro-static and magnetic fields.
- No Sacrifice of Quality For Price- Rigid laboratory and field tests on every component insures long-life trouble-free service.
HERE’S PROOF OF ITS RUGGEDNESS
… dragged behind swiftly moving autos:
It is estimated that the Model 404 Microphone withstood over 35,000 separate shock impacts during a 3.3 mile test drive at a speed ranging from 20 to 30 miles per hour. This is far greater punishment than would ever be required of a microphone in a life time of abnormally severe handling.