Abstract: An electronic exchange system comprising a telephone exchange for connecting at least extension lines and office lines, and at least an extension terminal which can be connected to the exchange, which has keys and can function as a communication device is disclosed. The terminal has a first memory device for storing key-assign data consisting of the codes of the keys, a data-receiving device for receiving the key-assign data, a memory control device for writing into the first memory device the key-assign data received from the telephone exchange, and a first control device for retrieving a key code from the first memory device and supplying the key code to the telephone exchange when the key identified by the key code is operated.

Abstract: A data error detecting method and system which can detect whether or not there occured an error in data stored in a memory of a computer system or the like. A new error check sign is introduced in addition to a prior art check sum sign to detect the data error on the basis of the both signs. The new error check sign is generated by applying weights that are different for different addresses in each of data blocks to the associated numbers of "1's" or "0's" of data stored at the addresses, multiplying the values of the addresses to the associated weighted numbers of "1's" or "0's" and then adding the multiplication results together.