Solution:

For the 232CLDRThe output impedance is 235 ohms,and the input impedance is 95 ohms (Vdrop will be about 1.86V with 20 mA applied) The max voltage drop is 2.2 Volts. Logic state Voltages used Receiver: Low: <= 4.8 mA 4.8mA < invalid < 5.2 mA High: > 5.2 mA Transmit: Vin = +10V ---> I out = 20.75 mA Vin = -10V ---> I out = 0.4 mA