The breakdown voltage is the voltage that the contacts are capable of withstanding where no breakdown or arc-over will occur. The insulation resistance is the resistance across the contacts and/or the resistance between the coil and the contacts. For a reed relay it is typically as high as 10 TΩ (1 with 13 zeros following it). Common reed relay applications can require many tens of millions of switching operations. Testing the contacts dynamically is critical to determine if there are any tiny flaws in the reed switch which can result in early life failures. This is a very important parameter for long, reliable, reed relay life.