Patent GB-966690-A (GB)
Title: Improvements in or relating to telecommuncation exchange systems
Inventor: KNIGHT RONALD GEORGE
IPC: H04M3/54
Filed: 1960-05-20
Abstract: 966,690. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd., and AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. May 19, 1961 [May 20, 1960], No. 17996/60. Drawings to Specification. Heading H4K. In an exchange containing transfer means whereby calls to a subscriber's line may be diverted to a predetermined other subscriber's line, this facility can be put into effect without any physical change in the exchange wiring being necessary. As described in a system of the type described in Specification 940,016, the magnetic drum carries a transfer track. which is used for the following functions (a) direction of a call from one subscriber's number to another; (b) night busying of P.B.X. lines; (c) service interception. Words are set aside in pairs for these functions and in case (a) the first word contains in bits TA1 ... TA16 the line identity and a bit in TA20 and the second word contains in bits TA1 . . . TA16 the identity of the line to which calls intended for the first line are to be diverted. Provided just four digits have been received and staticized on an incoming call, these are compared in turn with all the odd words of the transfer track. A trigger operated at the beginning of the comparison, stays up only when the comparison is successful and enables signals from TA18, TA19, TA20 to be staticized on appropriate triggers. In this case TA20 causes " transfer " to be staticized. The transfer digits in the succeeding word are also staticized. Under control of the comparison successful trigger and the transfer trigger, the original staticized line identity is deleted and the " transfer " digits substituted and these are now used for setting up the call. In case (b) the P.B.X. number is inserted in an odd word together with a bit in TA19. Moreover, a special " inhibit " class of service information relevant to each particular line of this type is provided and this is staticized. When successful comparison takes place and the bit on TA19 is staticized, this in combination with the " inhibit " class of service sets a " busy " trigger which inhibits the setting up of the connection and causes busy tone to be reverted. In case (c) the first word of a pair contains the number for which incoming calls are to be intercepted and a bit also occurs at TA18. This is staticized on successful comparison as described above and causes the selection of a special link circuit used for interception purposes and the identity of this link is registered. A signal is also sent to the channel selector to cause it to set up a call between the caller and an operator over the service interception link. Writing transfer record into transfer track.- The operator uses a special position of the type used for trunk offering and sets up a call in the normal fashion dialling a prefix 1 (to inhibit an " end of dialling "signal which would otherwise be sent by the register after receipt of four digits) followed by the identity of the line, an instruction digit and also if the transfer function is to be used the transfer digit. If the instruction digit signifies a writing-in operation (i.e. has a 1 in the first second or third binary position and a 0 in the fourth binary position), a trigger is set to enable a search to be made for a free word pair as indicated by a 0 in TA18 (this position may vary for different tracks if there are more than one) of the even word. When such is found, a trigger operates to prevent further tracks being tested. The bit enables a further trigger associated with the track which enables gates leading to the write head of the transfer track, which gates are held open for the succeeding odd and even words during which the staticized digits are fed to the track in TA1 . . . TA16 (line identity), TA18 ... TA21 (instruction digit) of the first word and TA1 ... TA16 (transfer digits) of the second word.