Patent GB-1193369-A (GB)
Title: Information Storage Arrangement
IPC: H04Q3/00
Filed: 1968-09-18
Abstract: 1,193,369. Automatic exchange systems. INTERNATIONAL STANDARD ELECTRIC CORP. 18 Sept., 1968 [22 Sept., 1967], No. 44282/68. Heading H4K. Equipment numbers for a pbx line group are stored in a sequential set of storage compartments, the group being accessed in response to a group directory number which results in read out of the compartment associated with the first line of the group, hunting over the remaining lines of the group being equalized by jumping from the first line to a line which is a random number of lines ahead in the sequence. A store M,which may be a ferrite core matrix, has 16 bit compartments for lines requiring special treatment such as pbx lines or lines having a special directory/equipment number relationship. The first six bits of each compartment indicate the type of information stored such as that a line is the first line of a pbx group and and indication as to the size of the group. The remaining bits for pbx groups store equipment numbers from which the lines may be rested for idle/busy conditions, the equipment number of the first line of a pbx group being the same as the directory number. A translator IC provides equipment numbers for normal lines and identifies those directory numbers requiring access to data in store M. A directory number of a pbx group is converted to binary form and transferred from IC to a logic circuit LNW which starts up a binary counter AD to scan the compartments of store M, the compartments being read out in sequence to a store RE1. When the number in LNW matches the number recorded for a line in a compartment of M, the first six bits in the compartment indicate to LNW that this is the first line of a pbx group and two of the six bits indicate the size of the group, the number is set up in store OC from which an idle/busy test is conducted. If the line is busy pbx hunting is initiated by LNW which on the basis of the size of the pbx group obtains the first one, two, or three, least significant bits of a binary number currently set up in a cyclically driven binary counter CNT. This randon number is used to fix a starting point for hunting over the compartments of the phx group in store M. If the random number is required to be more than 3 bits long an extra compartment below the compartment of the first line indicates the number of bits to be employed. LNW now proceeds to extract the address of the compartment next in sequence to the compartment of the first line and places this address in store RE2. Counter AD is now stepped idly until it addresses the compartment indicated by the random number obtained from CNT and the address of this compartment is set up in store RE3. From this point the equipment numbers of lines read out from further compartments of the pbx group are set up in OC and busy/idle tests are made. If to the end of the group no idle line is found, binary counter AD is set to extend the search from the address in RE2, which is the compartment of the second line of the group, AD addressing the compartments sequentially until, if no line of the group is idle, the compartment from which hunting began, as determined by the random number and set up in RE3, is reached. A comparator CD coupled to AD and RE3 determines when the starting point is regained and instructs LNW to terminate hunting.