The QTU is a throttle circuit to function as four throttles.

The four circuits can be linked or independent.

They can be:

1. Plain voltage controlled.

2. Feedback controlled.

3. Fully manually controlled as a conventional throttle.

4. Semi-manual or autonomous like BloNg/SuperBloc/BC3

5. Fully autonomous, including auto route setting.

6. Computer controlled.

7. Any mixture of the above.

The circuit uses a microcontroller to provide the required intelligence, and
this replaces some of the normal analogue circuitry found in feedback
throttles.

The microcontroller used is an Atmel AVR 90S8535 that runs at 8MHz and
provides 8 MIPS (million intructions per second).

Controls can arrive from any of the following:

1. Local potentiometers connected to any of the 8 user-defined analogue input
lines. These can be used as speed control, inertia setting or station stop
controls.

2. Local switches connected to any of the 32 input lines. These can act as
brake, reversing, or any function that can be configured within the unit.

3. Link wires from adjacent units (BloNg-like) on the same input lines.

4. Data received over any of the 8 serial comms lines from adjacent units
(this function not implemented in firmware yet).

5. Data received from a computer on RS232, RS485 or uplink RPC stack.

6. Data received from a control panel via RPC PTP.

7. Decisions made using the internal user-defined logic functions.