Abstract: A private branch exchange has optional service modules for providing optional service functions. The optional service modules are initially disabled, but can be enabled through a telecommunication link, in reply to owner information furnished by the private branch exchange. If the owner information is incorrect, the optional service modules can still be enabled, but the owner information stored in the private branch exchange is altered to leave evidence of the enabling operation. The enabling is carried out by remote authorization equipment according to an authorization key that specifies both the required optional service modules and the owner information. The authorization key is stored on a data medium that can be read only once.

Abstract: An error correction system for a difference set cyclic (272, 190) code with 190 data bits and 82 test bits in a packet which is transmitted on a vertical blanking interval of a television signal has been improved. The present system comprises a buffer memory for storing an original data which is subject to correction and corrected data, and an error correction circuit having at least a syndrome register, a majority circuit and a data register. The data transfer between the buffer memory and the error correction circuit is effected by wired logic hardware means without using software operation time of a programmed computer so that computer operation time is not wasted merely for error correction.