Patent GB-884394-A (GB)
Title: Improvements in or relating to automatic telephone systems
Inventor: PARIS HOWARD VAREY
IPC: H04Q3/00
Filed: 1957-04-18
Abstract: 884,394. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. April 2, 1958 [April 18, 1957], No. 12653/57. Class 40 (4). In a group selector comprising a uniselector the wanted group of outlets of which is marked by a digit switch which responds to a received impulse train, the reception by the digit switch of the second, and each subsequent, impulse of the train causes one of the contacts of the first, and successive groups, respectively, to be marked and the uniselector to be driven thereto while the dialling relay is still operated. The uniselector employed is a high-speed motordriven uniselector TS (Figs. 1-4) having sixteen banks of 51 contacts each, the angular displacement of the single-ended wipers of the pairs such as TS1, TS8 ensuring that 102 contact positions are traversed per revolution, of which the first 51 are termed the first half, and the second 51 the second half. All the first half and the first 47 positions of the second half correspond to working outlets, the remaining four positions corresponding to a test line TL, number unobtainable, busy, and home, respectively. The digit switch DS is a reverse-drive 25-point uniselector having two home positions 1 and 13, contacts 2 to 11 and 14 to 23. corresponding to digits " 1 " to " 0," and contacts 12 and 24 to a special train of eleven impulses for obtaining access to the test line TL. Banks DS2 and DS5 relate to group marking and prepositioning of the motor-uniselector, respectively, contacts 2 to 11 and 14 to 23 of the former bank being connected to the group marking terminals GMT1 to GMT0, and contacts 3 to 12 and 15 to 24 of the latter bank to the pro-positioning marking terminals PPT1 to PPTO. With the exception of those corresponding to the last outlets of each group, the contacts in banks TS15 and TS16 relevant to each working group are commoned and strapped to the appropriate one of GMT1 to GMT0, the last contact of each group being individually wired to the appropriate one of PPT1 to PPT0 Bank DS3 provides overflow metering facilities. Bank DS4 determines at what stage in the reception of the digit the first pre-positioning takes place. As shown in Fig. 3, the contacts 2 to 12 and 14 to 25 are commoned, but the rule is that this commoning should be cut in both ports at a point immediately following the contact corresponding to the first working group, except when outlets preceding that group are held in reserve for one or more future working groups, in which case the commoning remains intact. It will be assumed that all of the ten groups to which the group selector gives access are working groups and that the commoning is cut between contacts 2 and 3 and between contacts 14 and 15. The selector, when idle (resistance battery on lead P), is seized by grounding the P lead, ground applied to DL bringing up B, which locks to the P lead. Relay A repeats incoming impulses to set the digit switch DS, CD coming up for the duration of the train, together with its relief relay PP. If the digit is " 1," then upon the release of CD ground is extended over DS4 contact 2, the series-connected windings of high-speed test relay T, DS2 contact 2, and terminal GMT1 to all the contacts but the last of group 1 in bank TS15, and via the strapped terminals AT1 and BT1 and terminal PPT1 to the last contact of group 1 in bank TS15. The same ground is applied over the back contact of T to operate the latch magnet LM to start the motoruniselector, whereupon the test relay T is presented successively to the P leads of the group 1 outlets appearing in bank TS7. Resistance battery on the P lead of the first free outlet operates T, which stops the uniselector and operates H and HA to effect throughswitching. Received digit exceeds " 1 "-pre-pesitioning of uniselector.-The re-operation of A to the second impulse re-energizes CD, and when A again releases, DS advances to position 3, whereupon, while CD is still up, ground is connected over DS4 contact 3 to the latch magnet LM and to relay T, whence it is extended over DS5 contact 3 to PPT1, thus marking the last contact of group 1. At the same time, battery at resistor R1 is extended to wipers TS15 and TS16 so that T operates to the last outlet of group 1. With CD still up H cannot be operated. If the digit is " 2," CD releases with DS at position 3 and the uniselector wipers on the last outlet of group 1, and as soon as the front contacts of CD open, relay T releases at high speed to restart the uniselector, the closure of the back contacts of CD and PP completing the test circuit for all the outlets of the second group. If the digit exceeds " 2," the third impulse re-operates A which holds CD, and at the end of the impulse DS advances to position 4 with CD still up. The stepping of DS releases T and transfers the marking from PPT1 to PPT2 to mark the last outlet of the second group, to which the uniselector advances. Similar action takes place on the receipt of each impulse, CD releasing after the last impulse to initiate hunting over the wanted group. Spare codes.-These may relate to groups of outlets reserved for eventual use, viz. outlets allocated but not equipped, or to void digits for which no outlets are allocated. The GMT terminals relevant to all spare code digits are strapped exclusively to terminal SC which extends to contact 49 of bank TS16, N.U. tone being connected to the corresponding contacts of TS8, TS9. The straps between pairs of terminals AT and BT having the same digital significance are cut, the BT terminals relating to void digits then being strapped to those of the immediately preceding working group, whereas those of reserve outlet groups remain isolated. Modified selector circuit for use with relatively small outlet groups.-This circuit, which differs from that described above in that relay PP and the connections between the DS2 and DS5 banks via terminals AT and BT are not provided, causes the uniselector to be pre-positioned, in general, to the first outlet of the group immediately preceding that corresponding to the number of received impulses. The rules regarding the commoning on bank DS4 are different. The commoning of contacts 2 to 12 and 14 to 25 is cut at a point immediately following that corresponding to registration of the second working group digit if (a) at least " 1 " and " 2 " relate to working groups, (b) the first working group digit is preceded by a void digit or digits only, or (c) " 1 " is a working group digit and only a void digit or digits intervenes between it and the second working group digit. If the outlets of the first working group are preceded by outlets reserved for one or more other digits the commoning remains intact and the uniselector is pre-positioned to the last reserved outlet as soon as the first impulse is received. If " 1 " relates to a working group and a group of reserve outlets intervenes before the second working group, the commoning is cut between 3 and 4 and between 15 and 16, pre-positioning to the last outlet of the reserve group taking place on reception of the third impulse. The bank contacts (without any exceptions) relevant to each working group in banks TS15, TS16 are commoned and strapped to terminals GMT1 to GMT0, respectively, and the corresponding terminals of GMT1 to GMT0 and PPT1 to PPT0 relating to working groups are strapped. The group marking terminals relating to all spare codes are strapped to SC, and in the case of reserve groups the commoning for the group is omitted and the last reserve outlet in TS15, TS16 is strapped to the corresponding PPT terminal.