459,465. Telegraph exchange systems. LORENZ AKT.-GES., C., 1, Lorenzweg, Tempelhof, Berlin. Dec. 20, 1935, No. 35347. Convention date, Dec. 21, 1934. [Class 40 (iii)] In a system in which a subscriber is associated through an exchange with a " counter station" which can be called by dialling a single digit, and with other stations which can be called by dialling a series of digits, the line can be cleared by the calling subscriber only, the clearing-key ST being short-circuited at n1 unless the subscriber has originated the call. The calling subscriber can call the counter station alone by dialling 1 after operating the ringing-key, or he can call a distant station alone by dialling 3 before selecting that station, or he can call both the counter station and a distant station by dialling 2 before selecting. The invention is described as applied to an automatic exchange system but is also applicable to a manual exchange system. Effect of ringing-key. A subscriber A begins a call by closing the ringing-key AT ; or in a modification he may operate a dial contact Nu. At his station magnet M operates and holds on; it short-circuits the telegraph transmitter contact SK during the selection process, and causes magnet N to pull up and free the clearing-key ST. At the exchange, with which is associated the counter station B, relays J and E operate and bring about the operation of relays X1, R1, E2, A1, B, C and O. The buzzer SU is thus connected through b8, b9 so as to send back a dialling tone to the subscriber's indicator Fh; the warning lamp BL1 at the counter station is lit ; and the dialling-contact N1 at the counter station is disabled at o, to prevent interference. Calling counter station alone. For this purpose 1 impulse is dialled after the above operations have been effected in response to the operation of the ringing-key AT. When that key was released, armature a2 fell back to the position shown and applied one impulse to the rotary magnet Dr ; at the same time magnet V operated. The single impulse is now dialled, moving wiper d on to its first segment and energizing relay Y, which sets up the connection between the calling subscriber and the counter station 9. The motor Mol is started through y6, M1, m12, m13, and the signal lamp BL1 lights up. The printer magnet EM1 is brought into circuit so that it can be operated by incoming messages through contact e1, while outgoing messages originated by contact SK1 can be sent back to the calling subscriber A through contact s3. As soon as the circuit is established relay S3 pulls up and brings about the operation of relays S2, D, Z ; buzzer SU is thus caused to send a " ready " signal to the calling subscriber, the call-meter Zh is brought into circuit ; relays U1, F operate so that spacing current is put upon the calling subscriber's line through u11, u12, and the buzzer SU is cut out at u15, u16. Relay S operates and by pulling up relays H, N, starts the motor Mo, cuts off the dial contact N, and restores magnet M, but the latter is slowrelease so that the transmitter contact SK remains short-circuited at m2 until the motor has made several turns. Messages from the subscriber's transmitter contact go to the printer magnet EM1 at the counter station through relay E with contact e, relay E2 with contact e2, and relay E1 with contact e1, while return messages from the central-office transmitter contact SK1 go through relays S3, S2. Clearing. The clearing-key ST1 at the counter station is short-circuited at w2 so that only the calling subscriber can clear the line. This he does by opening the key ST, whereby relays E, E2, E1, X1, B, S3, and C are restored in succession. Relay Y holds on, however, and relays Dr, AII co-operate to step home the rotary switch wipers e, d. Relay Y is thereupon restored, and relays S3, S2, Z, D, U1 follow. The opening of the clearing-key ST also restores magnets S, H and N and stops the subscriber's motor M. Calling distant subscriber without counter station. For this purpose the first part of the procedure is as above except that 3 followed by the call number of the desired station is dialled instead of 1. When 3 is dialled, wiper e is stepped to its third contact, cutting off the relay Y and consequently the connections for the counter-station instruments. The singlegroup call of the desired station is then dialled and wiper d reaches the selected contact d1, after which relays V, U are restored; but before the slow-release relay has acted, relay P can test the c wire of the called station in a circuit through PI, PII, c to the winding RII corresponding to the called station, unless the latter is busy in which case contact b2 will be open. If the called station is free, test relays P, R pull up, and the a, b lines for the called station are connected at r1, r2, and relay S2 of the calling station operates relay Z ; but if the called station is busy so that relay P does not operate, relay Y operates to bring in the counter station, its circuit being in this case closed over u2, p4, as soon as relay U releases. Calling distant subscriber with counter station in leak. For this purpose the ringing impulse is followed by two dialled impulses and then by the dial number of the desired station. When 2 is dialled, relay X operates and locks, and an extra step is then given by rotary magnet Dr which is energized through x3, u1. The desired subscriber is now dialled as before, but now that contacts x1, x2, are open, the return impulse from the called subscriber frees the relays E1, S1, the relay S2 causing the relay X to operate ; and messages passing between the subscribers are relayed through contacts e1, s1, to the counterstation printer magnet EM1, while outgoing signals from the counter station are cut off at p1. Time control of connections. If a call is not completed a contact 20<11>, which is closed after 20 seconds, fails to be short-circuited at z5. Relay Y then operates and connects the counter station as above, the meter Zh being connected at y8. Call originated by counter station. The process is analogous to that described above but the relay W fulfils the functions fulfilled at the subscriber's station by both relays M and N.