BSD-340-user-guide-eng, Doc. 1004474-2, 2020-09-18,
Autronica Fire and Security AS
Page 6
2. PowerLoop – how it works.
NOTE: This chapter is intended for experienced professionals with knowledge about AutroSafe,
AL_Com, loops and LoopDrivers. Please refer to the following documentation for more
information:
• System Design and Engineering- 116-P-SYSDEENGIN-IFG/XGB
• System Description - 116-P-ASAFE-SYSTEMD/EGB)
2.1 Powerloops versus normal detector loops
PowerLoop was designed as part of the «Integrated Fire and Gas» functionality for AutroSafe. The
BSD-340 PowerLoop Driver communicates with Powerloop units through AL_Com, the same way
regular loop drivers (BSD_310) communicate with regular loop units. However, unlike the BSD-
310 Loop Driver, the BSD-340 PowerLoop driver handles the loop locally, and reports to the
system operator without involving AutroSafe’s loop handling module.
2.2 PowerLoop
2.2.1 Electric properties
The PowerLoop, is a two-wire loop that can distribute power to gas detectors, up to 30V DC,
100W (3A). The maximum capacity of detectors or other loops units is 15. Each detector has an
internal loop switch, just like regular loop units.
Data signalling uses a “power line modem”, which is a radio signal transmitted over the loop
wires. This gives 1200 baud transmission, just like AL_Com loops. Similar to wireless radio signals,
PowerLoops may experience reflections and cancellations depending on the cable length and
layout – which means that transmitters must be powerful and receivers must be sensitive.
2.2.2 Software handling
A PowerLoop is “raised” the same way an AL_Com loop is raised:
1. BSD-340 powers the first detector from the A side
2. The detector sends a Restart message (serial number, detector type)
3. BSD-340 orders the detector to close its loop switch, powering the next detector
4. The procedure in point 2. and 3. repeats until the loop is closed
Some special cases:
1. If the BSD-340’s B terminal is reached, there is a “closed loop”
2. If no Restart message is received, there is a “loop break”
3. If two Restart messages are received, there is a “branch” (which is illegal on PowerLoop)
4. If loop power disappears immediately after a loop switch is closed, there is a “short-
circuit”.
This is noticed by the detector, which opens the switch again and sends a short-circuit
message to the BSD-340
5. After a loop break or a short circuit BSD-340 starts raising from the B side.
This will in most cases bring all detectors to live
When the PowerLoop is up and running, some issues may occur:
1. Periodic loop measurement detects a loop wire break
2. Periodic loop measurement detects a loop short-circuit
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