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The Sentry has been designed to help solve some of the environmental noise problems encountered in entertainment venues and working areas. The Sentry has connectors provided to interface with a range of equipment, plus internally selectable options to make the system as versatile as possible. Although its main application is to control mains power outlets in entertainment venues it is not restricted to this application. Basically any function that can be controlled by a relay or switch can be controlled by the Sentry. These may include disconnecting loudspeakers, switching passive
attenuators to reduce system volume or acting as the trigger into an active attenuator system. It is microphone driven and has its own microphone built in to minimise tampering. The Sentry also incorporates the facility to operate at two different sound level thresholds which may be selected manually, by a remote key switch or similar, or automatically by a time switch (switches not supplied). This allows a venue to operate at different levels at different  periods of the day. e.g. when near offices or shops. An integral timer is available as a cost option.

Entertainment Venues
Under the Environmental Health act entertainment licences can be at risk if a Local Authority decides excessive noise from entertainment venues is a nuisance.
But what happens in an entertainment venue when a live band or mobile disco is using their own equipment?
It is still the responsibility of the venue manager to ensure that the regulations are adhered to and this is now possible with the Sentry.
The permitted level of noise in any venue is determined by the local environmental health officer (EHO). The sensitivity of the Sentry can be set-up in accordance with any of these regulations.
If the permitted levels are exceeded in any venue where a Sentry is installed and the warnings ignored, the offending equipment will be disconnected from mains power. Re-connection is only possible by operating the reset button.
The Sentry has the advantage over other units in that it features a large bar-graph VU meter with 23dB range to give visual indication of the noise level in a venue. Anyone can see what the volume level is and how their actions are contributing to this level.

Industrial Application
The Sentry can be helpful with regard to legislation concerning Noise in the Workplace. One or more units can be used as display units indicating sound pressure levels or to switch on warning lamps or illuminated signs to advise the need to wear ear defenders, when the safe noise level is exceeded. The cut-off threshold can be set anywhere between 85dB and 120dB.

Sentry Mk2 

Sentry Mk2 environmental sound level controller

New features on the MK2 version:

  • New case design provides easier connections via cable entry knock-outs and screw terminals.
  • A choice of internal microphone (supplied factory fitted as standard) or optional
    external microphone.
  • Removable cover provides access to all connections and settings. Anti-tamper seals are provided.
  • Anti-tamper microphone circuitry is incorporated with a front panel indicator.
  • Dual mains voltage operation is standard (internally switchable).
    Provision to connect a security loop is provided. This may be required to detect open doors or windows that would impair the sound proofing of a building, etc.

The Sentry works in conjunction with a relay or contactor. The unit operates by supplying a continuous voltage to the contactor which is connected to designated power outlets. If the unit is tripped or should anyone disconnect the Sentry the power outlets will be disconnected.

The bar graph meter is colour coded from green to red, and indicates the volume level in the venue. The red section increases in size to aid viewing. While the meter is operating in the green section, with even an occasional peak into the red, there is no cause for concern. If the two red "WARNING" segments are lit this indicates that the volume level in the venue is nearing the permitted limit. A connector is provided so that a mains powered warning lamp or beacon can be connected which operates at the same point as these two red sections of the meter. This lamp or beacon may be situated in a remote position.

If the noise level is high enough to light the "over limit" section (3 red segments) of the meter, the noise has exceeded the permitted limit. If this is allowed to continue the unit will trip and remove the power to the contactor. Visual indication is provided by the lamp adjacent to the re-set button labelled "Power off". The unit must then be re-set manually in order to restore power.

The unit has its own internal microphone and can be easily adjusted to operate at different levels. A remote reset switch can be connected to the unit, via the auxiliary connector.

An optional 32 amp, fully fused, boxed contactor with low voltage interface is available. Added benefits are the extra safety and possibly lower installation costs stemming from the fact that only low voltage cable is required as a connection to the Sentry. 

Alternatively 220/240V AC is available from the Sentry to interface with 220/240V contactors or relays.

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