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• AI12 - Analog input 12-bit

To the processor. Converts up to 64 analog channels to a single digital value as requested by the processor. This is done by means of multiplexes and a single analog to digital converter. The channel address sets the multiplexes. A 10 V regulator and buffer provide the voltage for the potentiometers associated with the AI12.

There is one AI12 PCB in each RTU.

• AO12 - Analog Output 12 bits

Analog output to the machine. Converts digital data from the processor to analog signals for controlling power supplies and coil currents. It has eight output channels which have a capability of 0 mA to 10 mA, therefore they are current drivers. Three of the channels can be software configured to 5 V. These are used on the coil circuits.

There is one AO12 PCB in each control area.

• AO8 - Analog Output 8 bits

Analog output to the machine. Converts digital data from the processor to analog signals. These control motor and coil drive circuits. It is an eight channel board with outputs of 5 V.

There is one AO8 PCB in each control area.

• ASU - Automatic Sep-Up

• CAT - Customer Acceptance Test

The purpose of these tests is to provide a formal demonstration that the equipment has been delivered to the stated specifications and is in a satisfactory working condition to be accepted by the customer.

• DIE - Digital Input Encoder

The digital input encoder send signals to the processor. Up to 32 channels can be monitored, these are usually switch circuits. The PCB has a pull-up resistor to each input so that the open circuit voltage is about 13 V. All the switches are grounded to 0 V. This gives relatively high noise immunity to the system. Two Field Programmable Logic Arrays (FPLA) control eight output lines, the FPLA being a once only programmed device, similar to a ROM. The outputs often go to relay output cards which have most of the interlock circuit switches in them.

There is one DIE PCB in each RTU except for the ICCA B side, which contains an extra DIE for the PSS.

• EIM - Electrical Interface Module

Its PSU supplies the patient support system.

• FKP - Function Keypad

It is in charge of the start and termination of treatment beam.

• FPLA - Field Programmable Logic Array

It encodes some numerous inputs to the area it located and controls a smaller number of outputs.

• FPLS - Field Programmable Logic Sequencer

the same with FPLA

• FTM interface- Fast Tune Magnetron

It acts as the point of entry for all the control signals to the FTM Rack. This PCB performs some level shifting and buffering of control and monitoring lines.

• IGBT - Insulated Gate Bipolar Transistor

It is a three-terminal power semiconductor device primarily used as an electronic switch.

• HHC - Handheld Controller

• HME - Hardware Movements Enable

This PCB adds an extra level of switching into the gantry rotation and table height drive systems. The output is switched by signals from the HHC, Automatic Set-Up (ASU) switch and Start switch.

• HTC - HT power supply controller

It controls the amount of charge provided by the HT power supply system to the Pulse Forming Network (PFN). The HTC also includes circuits which provide protection against overcharging of the PFN and malfunction of the system.

• HTCA - HT & RF Control Are

Area 16

• ICCA - Interface Cabinet Control Are

Area 72

• IPV - Item Part Values

The control software monitors and controls the machine via potentiometers, switches, relays, and supplies. To accomplish this, the software is organized into small packages called Items.

In each of the Items, there are many parameters. These convert the data values to actual units, that is volts, amps, and degrees. There is a standard format for the layout of these parameters, which are called parts.

• IRC - Interlock Relay Cards

They are used to switch the 24 VAC interlock chains as they pass through the digital linear accelerator assembly. Each IRC has three connectors: PL1 and PL2 on the rear of the board; PL3 on the front. A ribbon cable connects PL3 to one of the control areas. Each IRC carries eight single-pole relays, and many of the relays are used in the HT1 and HT2 interlock circuits which actuate the HT contactors. Both of these circuits pass through the client interlocks and through a series of relays arranged so that one relay operates in each half of each control area.

• ISA - Industry Standard Architecture

It is a computer bus standard.

• LIB - Linac Interface Board

It is an ISA PCB that has been designed by Elekta®. It is one of only two special PCB in the TCC.

The LIB has five interfaces to external equipment:

Interface Purpose

MLC 1553 Link Serial communication with the MLC

MLC Video Composite video signal from the MLC camera

External power +5 V and ±12 V external supply

VGA driver power Used by CAT 5 video converters

The LIB has six interfaces to other devices in the TCC:

Interface Purpose

MLC video out MLC video signal cleaned by the LIB and output to the frame grabber via an external cable

Fan supply Power to four internal cooling fans and monitoring of fan speed

Control processor

watchdog Reset signal for control processor used for emergency shutdown relays

LCD module control Control signals to the LCD dose backup display module

Serial Coms Serial communication to the serial isolation pcb

• MTU - Multiplex Terminal Unit

Multiplexer Terminal Unit. Data and addresses from the RMX processor are transmitted to the machine through two serial link cables. The MTU read this information and if it is addressed to its particular Remote Terminal Unit (RTU) it decodes it, passes the data and address to the bus in the control area and sends an echo and status report back to the processor.

There is one MTU PCB in each RTU.

• ODI - Optical Distance mete

It is attached to an adjustable mounting located on the gantry arm. The device projects a scale to indicate the source-to-surface distance (SSD) over the range 75 cm to 170 cm to an accuracy ±3 mm.

• PCI - Peripheral Connection Interface

There are three additional PCI cards fitted to the TCC:

Card Description

Quad XVGA Provides four XVGA output channels, two for treatment room monitors, one for the console monitor and one for an optional monitor (external XVGA line drivers and receivers are required for connection to the treatment room monitors).

Frame grabber Captures the MLC video image for processing by the control processor. This card is fitted on the control processor side of the motherboard and is fitted to all TCC whether an MLC is fitted or not.

SCSI controller Services the two hard drives.

USB 2.0

Interface Provides five USB 2.0 sockets for connection to external devices

such as the UPS.

• PMD - Power Motor Drive

There is one PMD fitted to later machines circa 2012. Function is the same as the UMD but the card provides higher drive capability for the diaphragm rotation drive.

• PPG - Programmable Pulse Generator

All the pulses within the machine are produced in this PCB. It has a 10 MHz oscillator which is divided down to the required frequencies. Some outputs appear all the time, others only appear during treatment.

• PRF - Pulse Repetition Frequency

• PSB - Pressure Sensor Board Dose Pulse Transmitter

Houses a sensor to measure atmospheric pressure for dose pressure monitoring and correction. Used for iViewGT timing pulses.

• PSS - Patient Support System

• RHCA - Radiation Head Control Are

Area 12

• RIC - Reeling Interface Cabinet

Since 2012 the reeling post (Area 60) and the interface cabinet (Area 70) have been replaced with the Reeling Interface Cabinet (RIC).

• ROC - Relay Output Card

This has a number of relays of three types, some of which are solid state, that is PNP transistors. Most of its input signals come from the DIE card, but it can be addressed directly by the processor. There are a number of LED indicators showing which circuits are active on the PCB.

There is one ROC PCB in each RTU.

• RTU - Remote Terminal Unit

Each control area is built around a PCB rack with bus interconnections. It consists of two independent terminals, A and B, each with its own power supplies. It functions independently as regards interlocks and safety circuits, known as the Remote Terminal Units (RTU).

Each RTU operates on a command / response basis and normally is waiting for a command. Any traffic on the serial link is sampled and checked for a valid command directed to the particular RTU. If a valid command is detected, the RTU communication section becomes active.

• SBC - Single Board Computer

• SCC - Single Conditioning Card

Filters, offsets or scales the values of analog voltages before conversion by the AI12. Not all the signals pass through the SCC, it has only a 40 channel connection to the A to D converter.

There is one SCC PCB in each RTU.

• SIB - Servo Input Beam

All the ion chamber signals are processed in the SIB, which also has sample and hold circuits. The DC output signals are used to control the steering servos and field irregularity circuits. One of the pressure sensors used for the dose pressure monitoring and correction is mounted on this PCB.

• SSD - Source-to-surface distance

• TCC - Treatment Control Cabinet

The Precise linear accelerators are totally digitally controlled. The control software runs on a multiprocessor computer housed in a cabinet located in, or near, the control room. The control software can be run in two modes, Clinical mode and Service mode. This enables the machine to be used for patient treatment or for maintenance and repair.

• TCS - Treatment Control System

• UMD - Universal Motor Drive

The Universal Motor drive PCB can be configured to drive several different types of DC permanent magnet motors or steering coils. The demand control voltage is ±5 V and an output is only provided when the ‘enable’ input is pulled to 0 V. The speed of a motor is controlled by sensing the motor current and voltage. The current for a steering coil is controlled by sensing current only.

• UPD - Universal Power Drive

They are a modified version of the current UMD PCB used to supply the gun filament current and the Magnetron tuning electro-magnet.