I am learning about Data and Computer Communications from W. Stallings Book. But in terms of actual signals (Frequency, Wave Forms, Signal Strength, Signal Distortion, signal waveform, Attenuation, Distortions) topics, terminologies I am missing out some very fundamental concepts. And I can't even find out what are some books or resources to be look about this. Should I look in to some introductory Physics Books or Electronic Books, or any Links that will strengthen my understanding about these concepts from the very beginner level and slowing to the very advance level. So, any Links, Books or Resources are welcomed to be shared . Also any beginner book on Data Communication is welcomed. Note: Resource should contain those topics that will make me realize Stallings Book better from the very fundamental level. Thanks In advanced.