The trigger inputs can accept floating signals that are not tied to the camera ground.
To use an analog trigger switch that connects to ground when a trigger occurs:
Connect Pin 1 (Power) to Pin 6 (Trigger +)
Connect trigger switch between Pin 7 (Trigger - ) and Pin 9 (Ground)
More sophisticated examples using TTL logic are shown below.
Trigger Input Example - TTL AND Gate
Trigger Input Example - TTL Inverter
The figure below shows an example using an optical trigger where the optical sensor is used to trigger multiple cameras. Note that with such a device, there will be some noise as the signal is switched and the camera’s debounce clock should be reduced to 100KHz to avoid multiple triggers.
Trigger Input Example - An optical trigger and multiple cameras