419,189. Automatic exchange systems. MERK, F., and FULD & CO. TELEPHONUND TELEGRAPHENWERKE AKT.-GES., H., 136, Mainzerlandstrasse, Frankfort-on- Main, Germany. Feb. 22, 1934, No. 5891. Convention date, Feb. 25, 1933. Addition to 413,054. [Class 40 (iv).] In a system embodying the multipling scheme described in the parent Specification whereby the final selectors of each group are adapted to extend the normal traffic to a particular group of 100 lines and the overflow traffic to another hundreds group or to particular sub-groups of other hundreds groups, when all the final selectors normally serving the hundreds group containing the wanted line are busy, the group selector is prevented from hunting over the group of outlets to which it is numerically set and is stepped on to the group of outlets leading to the final selectors which take the overflow traffic to the appropriate hundreds group or to the appropriate sub-group of that group. In the latter case, the appropriate sub-group is determined by the tens digit, and the group selector responds to this digit and subsequently repeats it to the final selector. In both cases a signal is sent forward to the final selector to bring about an initial movement to choose the group of outlets allotted to overflow traffic. Construction of selectors. The 100- point selector of Fig. 1 has five banks V each accommodating two groups of 10 outlets. Five sets of brushes B are carried by a rack S and are spaced so that they are separated from the banks they serve by progressively increasing numbers of steps. The brushes are tripped by fingers F which are arranged on a spindle T in such a way that the first downward movement of the rack S brings the brushes opposite the corresponding fingers in succession. Fig. 2 shows a 200-point selector with ten sets of brushes and banks arranged in a similar manner. The rack S drops by gravity under the control of an electromagnet so that, according to the duration of its operation, the movement may be step-by-step or continuous. A sequence switch which steps at each energization and at each de-energization of its magnet controls the operation of the trip spindle T as it passes through a particular position. A further auxiliary switch becomes coupled to the rack after a set of brushes have been tripped. Specification 391,989 is referred to. In Figs. 4-8, contacts controlled by the rack (magnet F or F<1>) are indicated by the reference k, those of the sequence switch (magnet S or S<1>) by m and those of the auxiliary switch by n, the bracketed numerals indicating the positions in which the contacts are operated. 100-point group selector, Fig. 4, and 200- point final selector, Fig. 6. Each bank V, Fig. 1, of the group selector accommodates two numerical groups indicated by the digits 1 and 6, 2 and 7, &c., while each bank of the final selector accommodates ten lines of the hundreds group normally served and tens lines of the adjacent hundreds group for overflow traffic. Switching relay Q of the call-finder, Fig. 3, connects up line relay A and relay C. During impulsing relay V pulls up at the first break, and succeeding makes are repeated over the a wire to magnet F, the circuit including a condenser K to restrict the duration of the repeated impulse, while earth on the b wire connects up magnet S of the sequence switch which moves to position 1 at the beginning and position 2 at the end of the train. The group test wire g is earthed provided there is an idle final selector in the group, and S moves to position 4, the spindle T being rotated to trip the appropriate brush set. Magnet F operates and allows the rack to drop continuously. If the received digit is 1-5, S moves at once to position 6 and test relay P is connected up over 5m, In and responds in series with C<1> when an idle outlet is found. If however the digit is 6-0, the tripped brush set is still 5 steps short of the appropriate group, and S remains in position 4, the test circuit being completed over 5m, 2n after the rack has taken 5 steps. Magnet F<1> responds to the tens digit, and magnet S<1> then moves its sequence switch to position 2 in which the appropriate set of brushes are tripped. The units digit takes effect and S<1> advances to position 5, test relay P<1> being connected up to test the wanted line as S<1> moves through position 4. Ringing current is applied, and relay 7 pulls up on the reply of the called party and disconnects S<1> which moves to position 6. All final selectors busy in the appropriate group. The group test wire g is disconnected, and relay U(i) energizes in series with S and locks over U(ii). Magnet F receives a further impulse over 2u, 2m, and S advances to position 4 as before. An outlet in the next group is then selected. Relay U is disconnected by test relay P, and as it falls back sends forward an impulse over the a wire to energize relay U<1>(i), which locks over U<1>(ii). After the tens digit has been received, a fresh circuit is made over 1m, 1u<1>, n for magnet F<1> which moves the rack 10 steps to bring the selected brushes to the beginning of the lower half bank. The wanted line is then selected in response to the final digit as before. 200-point group selector, Fig. 5. An initial digit 1 or 2 determines which half bank the selected brushes are to search over. If this digit is 1, the rack moves one step and then advances further in response to the second digit. If the digit is 2, the rack moves two steps and circuit is closed over 1k, 2m for magnet F, which moves the rack a further 10 steps, S being held in position 1 meanwhile over contact f. After the hundreds digit is received, S moves to position 4 in which the group test is made. As in Fig. 4, the rack takes a further step if no final selector is available in the appropriate group due to the operation of U, which subsequently sends forward an impulse to operate U<1>, Fig. 6. The selected brush set is tripped as S passes from position 5 to position 6. 200-point group selector, Fig. 7, and 200- point final selector, Fig. 8. The final selectors give access over the upper half banks to a group of 100 lines and over the lower half banks to 10 sub-groups of 10 lines lying in different hundreds groups, the numerical separation of the latter being determined by the tens digits of the sub-groups. The normal operations of the selectors are generally similar to those already described with reference to Figs. 5, 6. All final selectors busy in the appropriate group. The group test wire g is disconnected, and magnet S fails to energize thereover, so that its sequence switch remains in position 2. The tens digit is repeated by relay A<1> to magnet F to select a fresh group of outlets and also to the tens register DI. S moves to position 4, the selected brushes being tripped, and remains therein on account of the opening of off-normal contacts 1wI of the register. Hunting takes place, and test relay P pulls up in series with C<1> in an idle final selector. Earth connected to the a wire energizes magnet F<1> allowing the rack to drop continuously through 10 steps. The units digit sets the units register DII in the group selector, and S advances to position 6, whereupon relay B, which operated upon seizure in series with U, falls back, while U remains held over off-normal contact 2wI. S<1> energizes over the b wire and moves its sequence switch to position 1. Escapement magnet EI now interacts with J to restore the tens register DI, each operation of J sending an impulse over the a wire to magnet F<1>, until S<1> is released by the restoration of contacts 1wI and moves to position 2, in which the selected brushes are tripped. U falls back and S<1> reoperates and moves to position 3. Escapement magnet EII interacts with J to restore the units register DII, impulses being sent forward as before until contacts 1wII restore and allow S<1> to move to position 4. At the same time, S moves to position 8 to effect switch through. Testing and ringing of the wanted line take place as in Fig. 6. The registers may be associated in common with a group of selectors, and may be arranged for translation of the tens digit if the multipling scheme is such as to require it.