[Mark1960]

I just want to make some suggestions on setting up the scope to detect pulses that are not highly repetitive.

For TTL logic level signals like the pet, keep the trigger voltage at about 1.5v.

Select the channel with the least active signal for trigger input.

If the least active signal is mostly low, set the trigger to rising edge. If its mostly high, set the trigger to falling edge.

Try setting the trigger mode to trigger instead of auto. If there really is no activity this will give blank traces as nothing will generate a trigger, but you can select auto so you see the active trace.