[AgX]

Here is a circuit diagram of an opto-coupler based adapter for a Polaroid SX-70 camera.

Keep in mind that the SX-70 camera has a trigger voltage of 4.5 V, the typical AG-bulb trigger circuit would be at 15V. So that circuit would have to be corrected. Those 18Ohms resistors are related to Flashbar control and of no interest here.

http://www.sx2pc.com/



The choice of an opto-coupler enables switching quite high voltages. This approach would also be beneficial for a coupling device to trigger old style electronic flashes by modern cameras with electronic switching.
(I assume my SX-70 adapter contains a transistor.)