Siemens Cerberus PRO OOH740 — ASA Neural Multi-Sensor Fire Detector

What is the OOH740 neural fire detector?

The OOH740 is a point-type multi-criteria (multi-sensor) fire detector in the Siemens Cerberus PRO FD720 family. “Neural” refers to its ASAtechnology™ signal processing, which interprets the combined optical and thermal signals against the pattern and dynamics of a real fire — rather than reacting to a single raw threshold. The result is earlier detection of genuine fires and far greater rejection of nuisance sources like dust, steam and cooking aerosols.

A key strength is flexibility. Via software the OOH740 can be configured as a multi-sensor smoke detector, a pure smoke detector, or a heat detector, and its detection behaviour is selected through application-specific ASA parameter sets. It carries a built-in short-circuit isolator and a 360°-visible alarm indicator, and can run on an addressed C-NET line or — uniquely in this class — a collective or conventional line.

A closely related model, the OOHC740, adds an electrochemical carbon monoxide (CO) sensor, analysing three criteria (smoke, heat and gas) for even earlier detection of smouldering, CO-generating fires. This review focuses on the OOH740 while noting OOHC740 differences where relevant. For the wider platform this detector plugs into, see our Siemens Cerberus PRO brand page.

ASAtechnology™: how the “neural” detection works

ASA (Advanced Signal Analysis) is the intelligence layer that makes the OOH740 “neural”. Instead of comparing one sensor value to a fixed alarm level, ASA continuously fuses the multiple sensor inputs and evaluates them with static and dynamic algorithms selected by the chosen parameter set:

• Pattern recognition — the signal shape of a real fire (its rise, composition and dynamics) is distinguished from the signature of deceptive phenomena.
• Real-time situation interpretation — ambient conditions are assessed in real time to improve measurement accuracy and reduce nuisance alarms.
• Dynamic parameter influence — the algorithm dynamically adjusts within the parameter set as conditions change.
• Time- and process-controlled switchover — parameter sets can switch automatically between, for example, “manned” and “unmanned” states so the detector suits spaces whose use changes through the day.

Because two optical sensors (forward and backward scatter) and two thermal sensors feed the algorithm, the detector reliably picks up all fire types — light or dark smoke, or fires producing little smoke at all — while the redundant sensor system improves both reliability and immunity to interference.

Sensor design & the opto-electronic chamber

The OOH740 works on the scattered-light principle using a high-quality opto-electronic measuring chamber containing two optical transmitters, one optical receiver and two thermal sensors (the OOHC740 adds a CO sensor). The two transmitters illuminate any smoke particles from different angles: one acts as a forward scatterer and the other as a backward scatterer.

This dual-angle approach is what lets the detector respond well to both dark and light smoke particles — a known weakness of single-angle optical detectors, which struggle with the dark smoke of flaming fires. The chamber’s opto-electronic design blocks disturbing extraneous light while optimally detecting genuine smoke, and the two additional heat sensors raise immunity to deceptive phenomena and confirm developing fires. The whole detector is engineered to resist dust, fibres, insects, humidity, temperature extremes, EMI, corrosive vapours and vibration, and is shock-resistant with tamper protection.

ASA parameter sets: tuning the detector to the application

Rather than being a fixed device, the OOH740’s behaviour is chosen with parameter sets — pre-engineered algorithm profiles matched to an application. On the addressed C-NET line the detector offers seven parameter sets; in collective/conventional mode three are available, selected physically via the detector base or a parameter-set resistor. Representative sets:

Parameter-set availability and behaviour depend on line type, product version and configuration in the Cerberus tools. In collective mode, sets are chosen via base type (e.g. DB110/DB721D) or resistors PSR720-1 (33 kΩ = PS1) / PSR720-2 (68 kΩ = PS2).

Full technical specifications

Specifications from the Siemens OOH740 / OOHC740 data sheet (A6V10284161). OOHC740 differences are shown where they apply.

Three detectors in one: configurable detection behaviour

A major commercial advantage of the OOH740 is that a single part number can be software-configured as three different detector types, reducing stock-holding and simplifying design:

• Multi-sensor smoke detector — optical + thermal fusion for the widest, most reliable fire coverage with best false-alarm immunity.
• Smoke detector — optical-led detection where a straightforward smoke response is required.
• Heat detector — thermal-only operation for areas where smoke detection is unsuitable (e.g. very dusty or smoky-by-process spaces).

Combined with the parameter sets and manned/unmanned switchover, this makes the OOH740 unusually adaptable — one device family covering standard offices through to suppression-release and high-sensitivity critical rooms.

Applications and ideal use cases

Siemens positions the ASA neural detectors for demanding areas where earliest detection and false-alarm immunity both matter. Typical OOH740 / OOHC740 applications include:

• Data centres & IT/telecom rooms — the High Sensitive Fast profile for very early detection of overheating electronics.
• Hospitals & nursing homes — reliable detection with low nuisance alarms in occupied, sensitive settings.
• Restaurants & commercial kitchens — thermal fusion rejects cooking aerosols and steam that trip simple smoke detectors.
• Car parks & automotive workshops — the OOHC740’s CO channel adds early warning and toxic-gas monitoring.
• Heating/combustion & fermentation plants — environments with elevated CO risk suit the OOHC740.
• Suppression-protected rooms — the Suppression (PS5) parameter set gives dependable release behaviour.
• Sabotage-/tamper-sensitive sites — shock resistance and tamper protection with the optional locking device LP720.

An Ex variant, OOH740-A9-Ex, extends the neural detector to potentially explosive (hazardous) areas via SynoLINE300 / C-NET-Ex.

The OOHC740 difference: adding CO detection

The OOHC740 shares the OOH740’s optical and thermal system but adds an electrochemical CO cell, analysing three fire criteria — smoke, heat and gas. Because many smouldering fires (for example a mattress fire) generate carbon monoxide long before appreciable smoke, the CO input enables even earlier detection of these dangerous slow-developing fires. The CO signal is corrected for exposure, sensor sensitivity, temperature and ageing before being fed to the algorithm.

Importantly, the OOHC740 also provides an independent technical CO alarm channel: it can alarm on CO concentration thresholds separately from fire detection (“technical ambient supervision”), making it valuable where toxic-CO risk to occupants is a concern — heating rooms, combustion and fermentation plants, car parks, workshops, animal stalls and chemical labs. The CO channel’s detection behaviour is configured independently of the fire parameter sets.

Detector bases & accessories

The OOH740 uses the common FD720 base range — the base is ordered separately — and the same base type serves surface or recess wiring. Key options:

System integration: C-NET, Cerberus PRO & FIT

The OOH740 and OOHC740 run on the addressed C-NET detector line in the Siemens Cerberus PRO (FS720) and Cerberus FIT (FC360) fire systems, with automatic address allocation at commissioning and a built-in short-circuit isolator that keeps the loop running and locates faults between detectors. The OOH740 additionally supports collective and conventional lines (e.g. with FC10), which is unusual for a neural multi-sensor and useful for retrofits or mixed estates. Up to two external alarm indicators can be connected per detector, and a sounder base adds a local audible alarm.

Australian standards & AS 1851 servicing considerations

For Australian fire professionals, point-type smoke and multi-sensor detectors are covered by the AS 7240 series (Australia’s adoption of ISO 7240 / EN 54) — notably AS 7240.7 (point smoke detectors) and AS 7240.8 (CO fire detectors, relevant to the OOHC740). System design falls under AS 1670.1 and maintenance under AS 1851. The OOH740’s EN 54-5/7/17 certification generally underpins local acceptance; confirm the current Australian product listing before specifying. Practical AS 1851 servicing notes for the OOH740:

• Functional testing — test each detector’s smoke and (where used) heat response per schedule; the 360° alarm indicator aids visual confirmation.
• Contamination & clean/replace — the chamber resists dust ingress, but detectors in dirty areas should be checked and cleaned or exchanged using the DX791/FDUD491 tools for high-level units.
• Parameter-set verification — confirm the configured parameter set still matches the room’s current use (occupancy, process, suppression), especially after fit-out changes.
• CO cell life (OOHC740) — electrochemical CO cells age; verify the CO channel and plan cell replacement within the manufacturer’s service life.
• Isolator & indicators — confirm the built-in isolator and any external alarm indicators/sounder bases operate correctly.

Confirm the current edition of each standard and the applicable Australian approval with Siemens or an authorised partner before finalising design or maintenance.

Strengths and considerations

Verdict: where the OOH740 fits

The Cerberus PRO OOH740 is a genuinely versatile neural multi-sensor detector. Its four-sensor design and ASA signal processing deliver the two things that matter most in demanding point-detection applications — early, reliable detection and high immunity to false alarms — while its software configurability (smoke / multi-sensor / heat), seven parameter sets and manned/unmanned switchover let one device family cover a very wide range of rooms. The ability to run on addressed, collective and conventional lines is a practical bonus for retrofits and mixed sites.

It is at its best inside the Siemens Cerberus PRO / FIT ecosystem, where the C-NET features, parameter-set tooling and isolator are fully exploited. Where the fire risk is dominated by early smouldering or CO-generating events — kitchens, car parks, sleeping-risk occupancies — the OOHC740 variant is the stronger choice. For very large open volumes or high-airflow spaces beyond point-detector limits, an aspirating solution such as the Siemens ASD+ remains the better tool; the OOH740 is the high-performance point-detection counterpart within the same family.

This review is an independent technical summary. Cerberus™ PRO, Cerberus™ FIT and ASAtechnology™ are trademarks of Siemens. Specifications are sourced from the Siemens OOH740/OOHC740 data sheet (A6V10284161) and technical manuals and are subject to change without notice — always verify current model availability, approvals and standards editions with Siemens or an authorised partner before specifying or servicing equipment.

Standards & further reading

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