1 The sink current is limited by the current limiting resistor (R = 4.3 kΩ). 2 The current must be limited on the external device side so that the sink current does not exceed 50 mA. 3 This voltage depends on the pull-up resistance (Rpu = 10 kΩ) of the printer and the input resistance of the external device. Example input signal circuit I/O power (VCC_EX) I/O power (VCC_EX) Printer side External device side R External device output Printer input Example output signal circuit SG Printer side External device side I/O power (VCC_EX) External device input Printer output 20