Question: Bands employed in my venue won't play because they say that turning the power off will damage their equipment?
Answer: We hear this one quite a lot. People generally don't like being controlled in this manner and this is a good excuse, but the facts are that this is now the law and more and more venues are having to comply with noise regulations, whether we like it or not.
Of course playing below the allowable limit solves the problem!
But seriously, turning the power off on the majority of audio equipment does not cause a problem. But turning the power back on without notice can cause a problem.
Sound systems usually have to be turned on in a specific sequence. It is for this reason that a Sentry does not turn the power back on automatically and has to be manually reset. Therefore all that is required is to check that it is safe to reinstate power before resetting the unit.
Some computer-based systems don't like the power being switched off mid programme. It does not cause damage but can be inconvenient. If you wish to solve this problem supply a single mains socket fused at 2 amps and label it "TO BE USED FOR COMPUTERS ONLY". An audio system will require more power than can be drawn from this socket but computers don't require much power.
Question: Can the Sentry switch more than one power circuit?
Answer: Yes, one contactor can be wired to switch other contactors so there is no practical limit as to how many circuits can be controlled. We can also supply dual contactors which has two contactors installed in one case.
Question: Can the Sentry be made to turn the power back on automatically?
Answer: Yes, the Sentry can be supplied to auto reset but we do not recommend this for general mains
switching applications. Contact the factory if you have a special requirement.
Question: Can more than one reset switch be added to the Sentry?
Answer: Yes, remote reset switches are available as push button type or key switch type. Or you can
use your own; any low voltage push-to-close switch will work.
Question: If I hold the reset switch down will the Sentry automatically reset?
Answer: No. If a reset switch remains closed or a short circuit is present across the reset terminals, it will
not be possible to reset the unit until this has been removed and then the reset button pressed.
Question: Why are different weightings available on the Sentry and how do I know which one to use?
Answer: All the weightings refer to the frequency response of the measurement circuitry. Linear, as the name suggests is a flat response. When this is selected the response is flat with virtually no roll off at the very low frequencies.
Fig.1 shows the standard sound pressure level meter weighting curves.
There are three of them, 'A', 'B' and 'C'. 'A' is the most widely used when dealing with Health and Safety issues. The 'A' weighting curves principle effect is to decrease the sensitivity of the measuring instrument at low frequency to compensate for the hearing characteristics of the human ear.
However, when we come to the noise pollution problem, research has shown that entertainment noise pollution is predominantly caused by the rhythmic bass content and this will elicit most complaints.
Low frequencies are also the most difficult to prevent from escaping from a building. The 'A' curve is not suitable to accurately measure this low frequency noise so the 'C' curve or a linear response should be used.
Fig.1 also shows the response of the Sentry Bass option which when specified is fitted in place
of the 'A' weighting curve. The linear and 'C' responses remain unchanged.
Question: I wish to use a remote microphone. What type should I use?
Answer: Virtually any reasonable quality low impedance microphone will work, but for most applications we would recommend a good quality capacitor microphone, with an omni directional pick up pattern and a reasonably flat response. We can supply a suitable microphone if required.
Question: What is the level that the Sentry is set at when it leaves the factory, and will this need adjustment on site?
Answer: All Sentrys are factory set at the same level as part of our test procedures but it would be misleading to suggest that this level may be correct for a specific venue. The level the unit is set at will depend on several factors. E.g. where the unit is located in relationship to the noise source, the actual level which is allowed, etc. The only solution is to calibrate the unit on site.
Question: Although I have a Sentry fitted in my venue the level I have been allowed by the council is too low for the type of entertainment I wish to feature. What can I do?
Answer: The Sentry is not a cure all product. If your venue cannot adequately contain the level of sound you wish to produce, the, only answer is to improve the soundproofing of the building. Consult an acoustic consultant who specialises in soundproofing. Be aware that soundproofing is expensive and may not be viable in all situations.
Question: How do I adjust the operating threshold of the AVC2?
Answer: For the majority of applications this will not be necessary. The AVC2 will start to work at a signal level equivalent to the 0VU point on a standard VU meter, which is a convenient reference for operators. To achieve the required system level the output level of the AVC2 must be adjusted. If you do need to change the operating threshold level it is an internal adjustment. Consult the user manual.
