The Honeywell Morley-IAS MI-DISO loop isolation module protects analogue addressable fire alarm circuits by isolating localized wire-to-wire short circuits. Operating across an input range of 15 to 30 V DC with a quiescent standby current of 200 µA at 24 V DC, the module limits loop degradation. When an electrical fault occurs, the module’s bilateral solid-state switches activate within a fault detection delay of 100 ms to 400 ms, decoupling the faulted segment while maintaining continuous communication across the remainder of the signaling line circuit.
Zone and Floor-by-Floor Partitioning in Multi-Story Buildings
In commercial offices, high-rise residential properties, and healthcare complexes, life-safety standards mandate that an electrical short circuit on one level must not disable detection on adjacent floors. Deploying the MI-DISO module at zone boundaries allows fire system engineers to partition intelligent addressable loops into compliant segments. The module supports configurations with up to 25 addressable field devices—such as sensors and call points—between consecutive isolators. If mechanical damage, crushed cabling, or water ingress causes a short circuit on a single branch, the adjacent isolators drop open to restrict system downtime to that specific branch, leaving other operational floors fully functional on Morley-IAS ZX and DXc series control panels.
DIN-Rail Marshalling Cabinets and Control Equipment Integration
For installations where fire alarm cabling interfaces with central control gear, industrial automation racks, or plant distribution boards, the MI-DISO provides high-density circuit protection. When mounted to standard 35 mm DIN rails using the optional M200E-DIN adapter clip, multiple modules can be installed inside electrical enclosures to protect outbound branch circuits. The module's low switch-on resistance (0.065 Ω maximum at 15 V DC) minimizes loop line resistance and voltage drop, enabling long cable runs to remote plant areas without exceeding system thresholds.
Surface Deployment in Challenging Plant Environments
Industrial processing facilities, mechanical service rooms, and warehouses often expose field fire equipment to dust and variable temperatures. Rated for operation between -20 °C and +60 °C and non-condensing relative humidity up to 95%, the MI-DISO maintains reliable operation in non-climate-controlled spaces. When field mounted using the dedicated M200E-SMB surface box, ingress protection increases from IP30 (bare unit) to IP50, preventing particulate accumulation on the circuit assembly and plug-in screw connections.
Compliance Architecture Summary
| Deployment Parameter | Module Specification | System Engineering Consideration |
|---|---|---|
| Maximum Devices per Segment | Up to 25 addressable devices | Prevents widespread device loss during cable failure |
| Switch Isolation Response Time | 100 ms to 400 ms | Rapid fault isolation prior to total loop collapse |
| Loop Operating Voltage | 15 to 30 V DC | Standard Honeywell Morley-IAS loop power compatibility |
| Conductor Wire Accommodation | Up to 2.5 mm² | Supports standard fire-rated loop cable cross-sections |
| Mounting Configuration | M200E-SMB box or M200E-DIN clip | Enables IP50 wall mounting or 35 mm DIN rail integration |
| Diagnostic Visibility | Tri-colour LED in 2 planes | External status checks through M200E-SMB enclosure |
The MI-DISO fulfills life-safety architecture compliance requirements certified under EN 54-17 (CPR 0786-CPR-21643), LPCB, VdS (G202142), CEA GEI 1-084, and GEA GEI 1-082. Field technicians can verify operational status without opening the protective housing via the diagnostic tri-colour LED window and inspect decade address rotary switches across two planes during routine maintenance.
