Decoder and coder circuit

Claim 1

IN RADIO APPARATUS WHICH MAY RECEIVE INTERROGATION PULSES, MEANS FOR DECODING SAID INTERROGATION PULSES AND FOR PRODUCING A REPLY CODE IN RESPONSE TO SAID INTERROGATION, SAID MEANS FOR DECODING AND FOR PRODUCING SAID REPLY CODE COMPRISING A DELAY LINE, MEANS FOR APPLYING SAID INTERROGATION PULSES WITH A CERTAIN POLARITY TO SAID DELAY LINE, A UNI-DIRECTIONALLY CONDUCTING CIRCUIT CONNECTED TO A TAP POINT ON SAID DELAY LINE FOR CONDUCTING ONLY PULSES OF SAID CERTAIN POLARITY WHEREBY SAID INTERROGATION PULSES APPEAR AT THE OUTPUT OF SAID CIRCUIT WITH A CERTAIN AMOUNT OF DELAY, CIRCUIT MEANS TO WHICH SAID DELAYED INTERROGATION PULSES ARE APPLIED FOR PRODUCING AN OUTPUT PULSE IF THE SPACING BETWEEN INTERROGATION PULSES IS A CERTAIN PREDETERMINED AMOUNT, MEANS FOR ALSO APPLYING TO SAID DELAY LINE IN RESPONSE TO THE OCCURRENCE OF SAID OUTPUT PULSE A PULSE HAVING A POLARITY THE OPPOSITE OF SAID CERTAIN POLARITY, A UNI-DIRECTIONALLY CONDUCTING CIRCUIT CONNECTED TO A TAP POINT ON SAID DELAY LINE FOR CONDUCTING ONLY PULSES OF A POLARITY OPPOSITE TO SAID CERTAIN POLARITY WHEREBY SAID APPLIED OPPOSITE POLARITY PULSES APPEAR AT THE OUTPUT OF SAID SECOND CIRCUIT WITH A CERTAIN AMOUNT OF DELAY TO FORM THE REPLY CODE.