Recommendation: USE PIN 5 as Trigger and 7 as Strobe output.
GND is common for power, trigger +strobe
To initiate a TTL Trigger, apply a minimum voltage of 5V.
Basic circuits for Hardware Interfacing
Use Hardwaretrigger connection on IN1
For Strobe use OUT1
Use GND to make connection complete
TTL input circuit/ output ( i.e strobe )