When sourcing rotary switches, you must prioritize electrical ratings, including voltage (AC/DC) and current capacity (Amps), to ensure compatibility with your circuitry. Key mechanical specs include the number of positions (ways), number of poles, and the indexing angle (e.g., 30°, 45°, or 90°). For harsh environments, verify the IP Rating (e.g., IP65 or IP67) for dust and water resistance, and ensure the contact material (gold-plated for low current/signal, silver-plated for power) matches your conductivity requirements.