>>Application background: 1.RS485/232 take a long line, vulnerable to over voltage 2.RS485/232 line in the outdoor, vulnerable to lightning 3.RS485/232 is easy to be disturbed by other signals >>Program description and notes: 1 Front end uses a large flow of GDT, leakage current. 2 Back end using fast response time of TVS to clamp the voltage to low level, effectively protect the RS485/232 controller. 3 In the middle part of circuit to use PTC for decoupling, let the front end GDT action easily for discharge current. 4 This scheme meets the standards of IEC61000-4-2, GBT17626.2 and other static standards, such as IEC61000-4-5, GBT17626.5 and so on. 5 The same TVS and GDT are used in both modes of the differential and common in this program, and no protection dead angle 6 Meet 10/700uS (40ohm equivalent resistance) 1.2/50uS and 8/20 standards.
>>Program application: 1 Surveillance / Security system 2 Entrance guard system 3 Railway signal control lamp 4 Intelligent Transportation Systems 5 Meter / meter instrument 6 Optical switch/converter/tranceiver
>>Protection circuit diagram and product appearance:

>>PulseTake Protection Device
1 TVS1/TVS2/TVS3:SMBJ15CA
2 GDT: PTC471N (Mid-level lightning protection) PWF471N(High-level lightning protetction)
3 PTC1/PTC2: P250-120