System Architecture

TAPP is built around a simple idea: the equipment that must never be touched and the equipment that talks to the internet are physically separated, and the boundary between them is enforced by hardware, not software. This page explains that two-path architecture in plain language.

Two Physical Devices on Site

A TAPP installation places two distinct devices in the mechanical room, each with a different role:

• TAPP Gateway — a one-way data transfer gateway. It reads data from equipment control systems on its equipment side and passes that data, one direction only, to its network side. Nothing can travel from the network side back to the equipment side.
• Network Router — handles internet egress and the wireless sensor radio. It is the only device that talks to your network and to the cloud.

Path A — Controls / Critical (behind the TAPP Gateway)

Path A is for any critical equipment that has a control system — a boiler, a chiller, a water chemistry controller, or similar. Multiple pieces of equipment can share the equipment side of the TAPP Gateway; all of them are isolated from the customer network in the same way.

• Equipment controllers connect only to the equipment side of the TAPP Gateway. They have no connection to the customer network.
• TAPP reads controller data over Modbus TCP using read function codes only (FC3/FC4). Write function codes (FC6/FC16) are never issued.
• Data crosses the TAPP Gateway one direction only — outbound from the equipment side to the network side. There is no return path.
• The equipment side is accessible only by physical presence at the equipment. No remote path to it exists.

Path B — Wireless Sensors (network side only)

Where a control system isn’t present — or where you want additional coverage on tanks, motors, pumps, and other rotating or process equipment — TAPP adds wireless sensors. These live entirely on the network side.

• Sensors measure vibration, temperature, and pressure / current and communicate over a 900 MHz XBee radio network (Digi sub-GHz radio — not Zigbee, which is 2.4 GHz).
• The 900 MHz ISM band is chosen deliberately for industrial sites: longer range and far better penetration through walls, metal, and dense equipment than 2.4 GHz, so sensors reach the receiver from across a plant room without added infrastructure.
• Sensors report to a receiving radio on the Network Router, which collects their readings alongside the controller data. The sensors are self-contained measurement nodes; they carry telemetry only.
• Sensors are read-only. They observe equipment; they have no control capability and no connection to any control system.
• Wireless is deliberately confined to the network side. RF is treated as an untrusted medium and is kept off the equipment side by design.
• Worst-case impact of a compromised or jammed wireless link: a false or missing sensor reading. There is no path to the equipment side, and no safety event is possible.

Convergence and Egress

• Both paths converge at the TAPP network side, which publishes data to AWS IoT Core via MQTT over TLS.
• One AWS IoT identity and certificate per deployment.
• Traffic is NAT’d through the Network Router — one MAC address is visible on the customer network.
• Primary uplink is the customer’s wired network drop; cellular is automatic failover only.