Expert: Marc Ebelini - 10/28/2010

Question
dear sir
Plz tell me , what is the use of shift resister and clock used in ATC
transponder's encoder .  

Answer
While I do not fully understand you question I will have to make an assumption of what you are looking for. By clock you must be referring to the time base required in all computing devices. This determines the step by step functions as the processing chip reads the instructions. The faster the clock or time base the faster the devices can read the commands The shift register in any computing device moves the commands. When the register is full in moves the information stored to the next step. Let's follows this through step by step. A command requests that the ambient pressure is read. the next clock step shifts the reading received in digits form to the next clock step to decode it. the next shift register passes in on to the device that prepares it to be sent to the transmitting portion to send to the ground station. Lets take this in slow motion using a simple device. We have a 8X32 PROM. (programmable read only memory)
We can clock it using the 60 cycle power line frequency (clock)Each second causes the chip to present what is in the 8 bit register.
So every 32 seconds the 8 bit data will be transmitted. In this case it is the same information because it is only a read only device. in a complex system the data can be updated in each 8 bit register. so every cycle will present new data as in the case of the encoding device should the data change. In the case of PC's the clocks run in Hz. The speed of the clocks determine how fast the data can be updated. If the question involves the identification code only then the same thing applies. The ID code from the transponder display is sent because the data in the registers are static so each clock cycle repeats itself. Hope this is what you were looking for.