Castle GA902 | Sound sign

Contact Instrument Solutions

The Castle GA902 noise sign helps compliance with Health & Safety at Work Regulations. According to industrial safety law, areas subject to hazardous noise must be clearly defined, and workers notified of the danger.

In many cases, the noise hazard is intermittent - and that's precisely the situation the GA902 was designed for. It activates only when the noise exceeds a pre-set level allowing exposed workers to wear ear-defenders - often a less than popular safety measure - only when absolutely necessary.


Fitting the optional Mini-Beacon (GB003) greatly increases the warning impact, especially in larger areas where GA902A slave units can also be installed to provide complete coverage.

The GA902 is an essential part of noise control in engineering workshops, environmental and engine test laboratories, steel making works, generating stations, food and chemical processing plants, print shops, packaging and bottling lines etc. Applications outside industry have included warnings in discotheques.

A stainless steel weatherproof GA902 is also available for use in the food industry and outdoor situations.

The GA902 is a self-contained unit housing its electronics in tough steel, and is easily installed and set for action. The microphone is usually built-in but remote microphones can be ordered. The front panel text is available as standard in EC or USA forms, but can be ordered in any language and a variety of colours.

The front panel is completely blank when idle but brilliantly lit when activated to give an easily noticed warning. The addition of the optional Mini-Beacon (GB003) helps to ensure that all staff have been alerted.

The installation of slave units (GA902A) triggered by the master unit is advisable in large areas. Outputs from the master unit can also trigger other external devices, such as machines or process cut-off actuators - a complete system.


The microphone receives noise and passes it to the built in sound level meter where it is compared to the pre-set trigger level which if exceeded, switches on the twin fluorescent lamps to illuminate the warning sign. Once the noise in the area falls below the threshold for more than a pre-set time the lamps are extinguished.

Setting the trigger level

The unit is factory calibrated to 85dBA and a series of internal switches enables the user to select the desired trigger level in steps of ± 2.5dB.

Features overview

  • Self-contained unit
  • Easily installed
  • Mains powered
  • Fully automatic
  • Slave units available
  • Blank when off
  • Available with optional beacon


Measuring range 75 dB to 112.5dB steps switch selectable 2.5dB variable calibration control (factory set)

Trip time User adjustable 5 to 30 seconds

Controls Push to test button mains power ‘on’ indicator

Frequency weighting ‘A’ in accordance with IEC651 Type 2

Time response Slow response (1000 mS)

Outputs Switched AC power feed for external beacon; Change-over relay contact sets

Power 220V to 240V AC,50Hz/60Hz or 100V to 120V AC,50Hz/60Hz (Select on order)

Illumination Two 8W 300mm fluorescent tubes

Dimensions Overall: 520 x 200 x 120mm

Viewable screen area 450 x 190mm

Support documents

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Castle GA902 data sheet.pdf Castle GA902 data sheet
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