Electronic technology used in SIS

5 Electronic technology used in SIS N.5.1 Solid state relays 

Solid state relays are often used in high duty-cycle application and have unsafe failure modes that can be identified and quantified. Appropriate design features should be added to detect and alarm failures. Some additional applications of solid state relays are described in the following paragraphs. 

Solid state timers are used where the application s complexity does not warrant a PES. Solid state timer technology can be categorized as either Resistor-Capacitor (RC) circuit or pulse counting. RC timing devices may not be suitable for safety applications because of poor repeatability and unsafe failures. 

NOTE -- RC circuitry is often used in the time setting portion of pulse-counting timers. This does not preclude the use of these 

The pulse-counting timer, sometimes referred to as a digital timer, can use a number of methods to achieve pulse counting. These include 

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