The following inputs have fixed amplifier parameters:
- EA (External Arming) is fixed to 1 kΩ impedance and approx. 1.5 V trigger level;
- ER (External Reference) is fixed to 50 Ω impedance and accepts signals with 0.1 to 5 Vrms amplitude;
- C (Prescaler input) is fixed to 50 Ω impedance.