 Homing transponders are similar to IFF systems in general terms , but used shorter pulses . When a signal was received from the radar , the transponder responded with a short pulse on the same frequency , the original radar pulse would not be reflected so there was no need to lengthen the signal as in the case of IFF . The pulse was sent to the Mk . IV 's display and appeared as a sharp blip . Depending on the location of the transponder relative to the aircraft , the blip would be longer on the left or right of the azimuth display , allowing the operator to guide the aircraft to the transponder using exactly the same methods as a conventional aircraft intercept . 
