*6.1. Arduino Transmitter*

In the proposed communication system, the Arduino is considered as the core of transmission. Here, we employ the Arduino Uno R3 microcontroller boards, which are simple and implemented at a low cost. It has 14 digital input/output pins (6 of them can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, a USB connection, and a reset button [41].

First, we convert the signal from the bipolar form to the unipolar form, and this is due to the fact that the Arduino analog inputs only accept unipolar signals in the range from 0 V to 5 V. The communication starts with a message *M*(*s*), which is sent to the analog input A0 of the Arduino transmitter, as shown in Figure 9. Second, the input signal is converted from analog to digital using an embedded 8-bit ADC at a maximum rate of 8000 samples per second. Finally, this signal is encrypted by the 2D-ICSM and Delta modulator.

**Figure 9.** The transmitter circuit.
