Philips Avalon FM20, Service Manual

Page: 40 / 260

4 Theory of Operation
40
• Connector Block (1253-8415)
• Bus Master Board (M2703-66460)
• Main CPU Board (M2705-66510)
• Fetal Recorder (Thermal Printer Unit)
• Display Assembly (M2703-64503)
• Noninvasive Blood Pressure Board (optional, M2703-64502)
• SpO
2
Board (optional, M2703-66453)
• Input /Output Interface Boards (optional):
– LAN / RS232 (M2703-67501)
– Dual PS/2 (M8086-67501)
– MIB/RS232
– Flexible Nurse Call
– Quadruple USB ports
Power Supply
The power supply is a wide-range input switching unit, with an output of 24V. It is located in the
bottom housing assembly.
Connector Block
Any compatible fetal transducer can be connected in any order to the monitor via the sockets on the
Connector Block. The Connector Block is located on the Bus Master Board, and is exchangeable. The
assembly made up of the Connector Block and the Bus Master Board is referred to as the Front End
Assembly in the chapters “Repair and Disassembly” on page 139 and “Upgrades” on page 213.
Bus Master Board
The signals from the transducers or sensors are conveyed from the sensor sockets on the Connector
Carrier Board (M2703-66421) to the Bus Master Board (M2703-66420).
The Bus Master Board is responsible for transducer detection, communicates with the connected
transducers via a CAN bus, and communicates parameter data to the Main CPU Board via a serial link
for further processing and display.
Main CPU Board
The Main CPU Board controls the monitor’s human interface, and is responsible for the final
processing of data from the Bus Master Board. It sends this data to the TFT display, and to the
thermal printer unit for recording traces, and other patient data. It also controls the optional LAN/
RS232, USB, and PS/2 interface boards.