The connections on the front panel of the Shamrock series are shown below:
Figure 3: Front Panel Connections
Shutter
The shutter in the 500i/750 may also be operated by an external TTL signal. This allows the shutter to be operated by, 
and synchronised to, other laboratory equipment.
I/O
9 pin I/O connection.
Filter
15 pin connection to enable connection to optional lter accessories.
Filter (15 pin)I/O Connection 
(9 pin)
External Shutter 
Connection (BNC)