Abstract: An improvement in the present radar/IFF equipment used by the military whereby the transponding equipment, when used in crypto-secure Mode 4, is enabled to reply with its unique coded identification number (Mode 2 reply) after it has made its Mode 4 reply. This is accomplished by adding an AND gate and a delay means to the present equipment. The AND gate is connected to couple the Mode 4 three-pulse interrogation to the delay means if it is received at the same time the I/P activate switch is in its operating position. The delayed three-pulse interrogation signal is coupled to the encoder and activates a Mode 2 reply. The ground equipment is also modified to enable it to faithfully reproduce the entire video output of its interrogator section.