What is the difference between pulse code modulation and delta modulation? Provide examples.

Pulse Code Modulation (PCM) and Delta Modulation (DM) are both techniques used to convert analog signals into digital signals, but they operate in different ways and have different characteristics.

Pulse Code Modulation (PCM): PCM is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals. Each sample is then quantized to a series of symbols in a digital (usually binary) code. PCM involves three steps: sampling, quantizing, and encoding.

For example, consider an audio signal. In PCM, the signal is sampled at discrete intervals (like 44.1 kHz for CD quality audio), and each sample is then represented by a binary number. A sample could be quantized into a 16-bit value, giving 65536 possible levels of quantization.

Delta Modulation (DM): Delta Modulation is a simpler form of modulation compared to PCM. It encodes the difference between successive samples rather than the absolute value of the samples. In DM, only one bit is used for each sample; this bit indicates whether the signal is increasing or decreasing from the previous sample. The encoder adapts to the rate of change of the input signal, and the granularity of each step is fixed.

For instance, consider transmitting a slowly varying audio signal. In DM, if the signal level increases slightly, the output bit would be a '1', indicating an increase, and for a decrease, the output bit would be a '0'. Because of using only one bit per sample, DM is not as precise as PCM but can be more efficient for certain applications.