I am trying to confirm a suspicion/understanding about electrical signals, and especially One-way CONTROL signals i.e. specifically NON-Power type signals in electronics like,
- Trig/Echo pin in UltraSonic Sensor,
- Digital IO line on an application specific IC/Sensors feeding into a microcontroller via high speed buses.
- High Speed USB Camera connected via Serial Tx/Rx
which DO not EXPLICITY require a DEDICATED Ground (unlike power signal which requires a ground connection to function), but IMPLICITLY always return via Ground/PCB Ground Plane to the point of origin.
In short, what I am trying to confirm is that, no signal (control or power) is ever one way, and MUST find a way back to its origin to complete its journey. In practice, we observe this on PCBs with ground planes, as every signal will find its own path back, usually right under the trace, on the ground plane underneath.