Edition 8

Syncro Analogue Addressable Fire Control Panel

Syncro AS Analogue Addressable Fire Control Panel

Kentec Addressable Control Panels –
400mA Loop Current

The desire for more addressable loop beacons and sounders to be fitted on to each addressable control panel detection loop circuit has resulted in a market demand for higher current capacity loop drive circuits.

Whilst the ability to provide higher loop current to drive sounders and beacons is useful, there is a penalty in increasing the current capability of the loop. As the loop current increases, the effect of loop cable resistance, inductance and capacitance on the panel to detector signalling becomes more significant.

The overall result of increased loop current is a reduction in the maximum permissible cable length for the detection loop.

Table showing typical reduction in loop length with increased loop current (1mm cable)

This table shows that there is a balance between loop loading and loop length. It is considered better practice to provide many low volume (low current) sounders evenly distributed around a reasonable length loop, rather than a smaller number of higher volume (higher current) devices on a smaller loop.

If there is a requirement to provide high loop current over longer loop distances, then the cable cross section area must be increased, resulting in a more expensive installation cost.

Using 400mA as the maximum available loop current, the Kentec control panels offer sufficient capacity to drive a reasonable number of devices over an acceptable loop cable length.

Typically the 400mA loop current is sufficient to fully populate a loop with loop sounders at 85dB, or to fit at least 50 sounder and loop beacon combinations at 85dB.

For full verification of loop designs, always use the loop calculation applications, which can be downloaded using the following links:-

Apollo loop calculator:

Hochiki loop calculator:


Sigma Si Status Unit

Sigma Si Status Units –
Monitored Mode and Hold Inputs

The Sigma Si status unit has the facility to connect remote Hold off and Mode select inputs directly to the status unit. These inputs are fully monitored for open and short circuit cable faults.

This facility on the Sigma Si can provide considerable installation cost saving, in particular with the provision of door interlocks. In most cases the status units are installed adjacent to entrances to the protected area and therefore it is considerably more effective to wire the door interlock to the status unit, rather than install a dedicated 2-core cable back to the Sigma XT control panel.

The same is also true of the Hold off facility, whereby the cable from the hold off buttons inside the protected area may be closer to the status unit than the control panel.

Both inputs to the status unit use a firing resistance of between 100 and 1000 ohms and a 6.8k ohms end of line monitoring resistance. Faults on these monitored inputs are reported at the Sigma XT panel and locally at the status unit by internal fault indicators.

Download the Sigma Si Datasheet:

Download the Sigma Si Manual:

This facility is available on ALL Sigma Si Status Unit models, including the new IP65 weatherproof range.

If you feel a colleague may benefit from receiving In the Technical Loop they can be registered for their own future copy by clicking the following link.

Kentec Electronics Ltd.
Tel: +44 (0)1322 222121 Fax: +44(0)1322 291794