Downloaded from https://www.everyspec.com MIL-STD-1311D Zin - Internal impedance of trigger circuit. Zext - External impedance added to trigger circuit. Zs - Zin + Zest. This is the desired source impedance including all circuit impedance. Rg - Thyratron grid return. is - Short circuit current. FIGURE 8. Trigger circuit (1). Zin - Internal impedance of trigger circuit. Zext - External impedance added to trigger circuit. Zs - Zin + Zest. This is the desired source impedance including all circuit impedance. Rg - Thyratron grid return. FIGURE 9. Trigger circuit (2). 12