Key Features & Functionality

• Built-in LCD: The unit has an onboard screen to display status/readings.
• Analog I/O support: Two analog inputs (for connecting to a propane-gauge sensor such as a Rochester R3D) and two analog outputs.
• Alarm / Relay outputs: Supports triggering relays when fuel reaches high or low thresholds — so maintenance staff can get alerted when fuel is low.
• Serial communication (RS-232): Includes an RS-232 port for remote or automated monitoring / control integrations
• Some versions are available with 48 V power support and 4-20 mA converters (useful for industrial control / SCADA-type monitoring systems).

Use Cases & Why It’s Widespread

• Because many telecom/radio towers rely on backup generators (diesel or LPG), it’s crucial that fuel levels are tracked reliably — the STM’s robust design, combined with alarm/relay + remote-monitoring options, makes it a “go-to” solution.
• Its “workhorse” status: the STM line (including STM94442A) is described as one of the oldest and most respected in MDi’s monitor suite — implying long-term reliability and field-proven performance over decades.

Typical Setup / Integration

• For propane (LPG) tanks: connect a compatible gauge (e.g. Rochester R3D) to the analog inputs.
• Use the analog outputs or relay outputs for integration with site-control systems (to trigger alarms or external logging).
• Use RS-232 for remote readings, telemetry, or logging fuel status in backend systems.