The use of nonexhaustive codes which have special types of redundancies are formulated. The properties of these codes include the ability to detect amplitude errors in binary sequences by driving the decoder into an error detected state. However, the errors are detected at some time after the error has reached the decoder and thus the name time delayed error detection, TDED. When an error is received, the decoder is found to be in one of three phases or conditions, in-phase, out-of-phase, or error-detected-phase. A type of nonexhaustive code called an even code, is capable of detecting any single error. An algorithm is presented which can construct an optimum single error detecting even code for any alphabet. This optimum even code is found to be very close in average code length to the Huffman code for the same alphabet. TDED codes which detect more than one error are included and a general theorem is proved about higher error detecting TDED codes. The hardware needed to implement a TDED system is dealt with and a phase check which checks to see if the decoder is in the in-phase condition is discussed. TDED codes are shown to be usable in most applications which require error detection.