Do Most Panels Change Their Circuit Polarity?

[goncall]

due to panel designs not catching up, especially on companies who made ther own 'in house' there was an 'in between' period where only the neg 'leg' was 24 hour, with the pos leg passed through door contacts etc. so only active when the alrm was armed

On the last co i worked for, the panel had a single e.o.l resistor circuit just for wiring and foil purposes, meant freeking miles of foil and frames on one zone , if you had a fault you first played 'find the eol resistor' for an hour or two .

you'd scoff at doing so now, but this as common practice, you were simply used to finding eol batteries, so searching for the ressistor was just another accepted practice.

Brocks (iirc) used a panel with where diodes were placed across the contacts, during the day the loop was montired as current passed through the diodes on open doors, when the panel armed zone voltage/s were reversed so an open door would prevent setting, its the only panel i know of that did reverse the zone voltages, not sure how they copped with BS.4737 for D/P and tamper needs, as i never actually worked on one.

as for 9100' simple DP zones, 9800's its a shared common + pole for each 2 zones, so if the alarm loop did change polarity when set as 24 hour or PAB zone, it would not comply with BS.4737 in that state having also a negative anti tanper loop, you would also 'loose' 2 D/P zones to achieve one 24 hour zone.

Arfur

thorn security panels did this,the 7002 and 7008,

[arfur mo]

im afraid not arf. If the circuit is programmed as PA it would indeed send a PA if that was required.

think our wrong - again lol!

iirc i believe that was stopped in BS.4737,

i.e. cable fault was not to send PAB.signal. in those D/P days that would be deemed a break on the Anti Tamper loop not causing PAB signal, local bells only and full alarm only when set (as an ant tamper would do normally).

i can't point to any reference but definatly remember discussing it at an IFSEC when it was held in London, the reason given for bringing in the rule was to cut out things like service engineer or builder removing the lid screw on a pab, or as happened the PAB loop being used as the Anti Tamper.

so i'll stand to be corrected, on G.595 a zone set as PAB from my experience if the zone is shorted creates a fault not a PAB action, as will a break. to get it to action as a PAB you need the correct resistance in the loop as is created when a C/C pab go's O/C i.e. eol + bridge resistor( = nominally 15k).

if the GAL actions a panic as you think on a short/break imho it is then not to BS/EN standards - unless it was dropped.

Arfur

[IAS]

the correct resistance in the loop as is created when a C/C pab go's O/C i.e. eol + bridge resistor( = nominally 15k).

.

Arfur

it`s actually 11.4K thats "eleven point four" for the terminally stupid.

[james.wilson]

sorry alan, your quite right a short would cause a tamper in that instance. I misunderstoood and thought you meant something else.

[IAS]

sorry alan, your quite right a short would cause a tamper in that instance. I misunderstoood and thought you meant something else.

mine?

[james.wilson]

mine?

re changing polarity.?

are you asking would you need a changing polarity to use n/o detectors?

[IAS]

re changing polarity.?

are you asking would you need a changing polarity to use n/o detectors?

no, I was waiting for my apology ............. LOL

still it`s the second most pointless topic I`ve ever seen on the board.

[james.wilson]

ok im sorry for you too

[IAS]

ok im sorry for you too

a less generous man could take that the wrong way ................LOL (again)

[james.wilson]

lol