MTL7728- is the 7700 series intrinsically safe zener barrier. MTL7728- 28V, -ve, 300 ohm for controller outputs, solenoids.

The MTL7700 Intrinsically Safe Barriers are 1- or 2-channel DIN-rail mounted shunt-diode safety barriers that use intrinsically safe explosion-protection techniques to pass electrical signals between safe and hazardous areas, while limiting transferred energy to a level that cannot ignite flammable atmospheres. Connected in series with wiring entering any hazardous area on process plant, MTL7700 Series barriers prevent explosions in all normally occurring explosive atmospheres – including mixtures of air with flammable gases, vapors, dusts and fibers – if a fault or faults develop in the safe area.
The specific price of the product shall be subject to the actual consultation.