CHAPTER 2THEORY OF OPERATION
This chapter describes the operating principles of the circuitry and printer mechanism.

1. Block Diagram ................................................................................................... 21

2. Main Logic Board .............................................................................................. 23

2-1. Data I/O Circuitry .................................................................................................. 23
2-1-1. RS-232C Interface........................................................................................ 23
2-1-2. RS-422A Interface........................................................................................ 24
2-1-3. Parallel Interface.......................................................................................... 25
2-2. Editing and Printing ............................................................................................. 26
2-2-1. Editing .......................................................................................................... 26
2-2-2. Thermal Head............................................................................................... 26
2-2-3. Head Current Control .................................................................................. 27
2-3. Feed-Motor Drive Circuit ...................................................................................... 28
2-4. Power-On Reset Circuit ....................................................................................... 29
2-5. +5V Line Voltage Detector Circuit ....................................................................... 30

3. Printer Mechanism ............................................................................................ 31

3-1. Thermal Head ........................................................................................................ 31
3-2. Paper-Feed Mechanism ....................................................................................... 31
3-3. Sensor ................................................................................................................... 32
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