Operation
TheSentryfeatures a large bar-graph VUmeter with 23dB range togive a visual indication ofthe
noiselevelinavenue. Thishastheadvantageoverotherunitsinthatanyonecanseethevolume
levelandcansee how their actions arecontributingtothis level. While the meter isoperatingin
thegreensection,with even an occasional peakintothered, there is no causeforconcern.
TheSentrywilloperate within the range 80dB-120dBand may be pre-set toanywhereinthis
range. Provisionis included to operate at2 differentlevels,for instanceatdifferenttimesofday.
Thisselectioncanbeperformedmanuallyorautomaticallybya time switch. Afrontpanel
indicatorshowswhenlevel2 is selected.
Ifa mains warning lamp isconnected it will operateat the same pointas the two redsections of
themeter. Thesearelabelled“WARNING”.
Ifthenoiselevelishighenoughtolightthe“OVERLIMIT”sectionofthemeter(threeredsections)
thenoisehas exceeded the allowable limit. Ifthis is allowed to continuefor more than the settime
periodthe unit will tripand remove thepower to the contactororrelay. Visualindication of this is
providedabovetheresetbutton.
Whenthe unit is firstpowered up theRESET indicator will belit - waitfor a few secondsand
pressthere-setbutton. TheSentrywillnowbere-setand ready for normal operation.
Theactionofthetimingcircuitmeansthatcontinuallyexceeding the limit even for short periods
mayeventuallytriptheunit.
Theunithasto be manually reset torestorepowerand this will only bepossibleaftera short time.
Theresettimeis determined by the amountbywhichthe unit is driven overlimit.e.g.tripping the
unitby just exceeding thelimit will resultin a short periodof a fewseconds before reset is
possible. Tripping the unitby grossly exceedingthe limit will requirea longer periodbefore reset
is possible.
NOTE. It is important that a check is made before the unit is re-set.
Check that it is safe to do so.
Audiosystems generally need tobe powered upin a specific order. In an audio system
comprisingofdifferent components amplifiers, mixers, etc.a general rule is toswitch power
amplifiers off first and on last to avoid possible loudspeaker damage. Therefore a band or D.J.
mayneedto turn off amplification equipmentto protect loudspeakers before thepower is
restored.
Mic Tamper
Ananti-tamper circuit is incorporated whichif enabled will detectthe presence of tapeetc. placed
onthecaseabovetheinternalmicrophoneinanattempt to artificially raise the internally set
threshold.Toenablethisfunctionadjust theT.S. preset (X) on Drg 879. (turn the pre-set to
approx the 11 o’clock position. External microphones being disconnected will also be detected
bya seperate circuit. Afront panelindicatorwillshow MICTAMPER.
TheSentrywillswitch off if the MictamperorSecurity loop indicators are illuminated.
Allconnectionsandadjustmentsarelocatedbeneaththeremovablecover plate. None reusable
securitylabelsaresuppliedwitheachunittohelpensure that unauthorised tampering is detected.
Timer
Theperiod of time thatnoise “over limit”is tolerated before theunit trips outis variable over the
rangeof 10 - 70 seconds. Apre-setis provided to adjust thisshould it be necessary - the factory
settingis approx. 20seconds.
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