604,917. Telegraph systems. TELETYPE CORPORATION. Jan. 15, 1945, No. 1196. Convention date, Dec. 20, 1943. [Class 40 (iii)] In a telegraph system, a transmitting station is provided with means for applying sequential message-identification markings to the record or records of the messages successively transmitted and for deriving signals corresponding to the markings thus applied and a receiving station incorporates means for applying like message-identification markings to a record or records of. the messages successively received and for deriving signals corresponding to the markings thus applied and means for automatically comparing the signals corresponding to the identification markings applied to records of the same messages at the two stations to indicate whether these markings are in agreement or at variance. As shown in Fig. 1, the perforated-tape transmitting apparatus comprises feeler levers 38 operating goose-neck transmitter contacts 36 under control of a cam-shaft 25 connected to a main transmitting shaft 18 by a toothed clutch 27 operated by the armature 29 of a magnet 32, Fig. 3. An auxiliary transmitting assembly comprising selector bars 74 is controlled by a cam assembly 26 connected to the shaft 18 by a toothed clutch 28 actuated by the armature 31 of a magnet 33. When clutch 28 is operated, a second shaft 24 driven at one-sixth the speed of the shaft 18, and carrying a cam 62, operates a pivoted lever 46 having a forked end supporting a numbering device 44 comprising a number of discs carrying letters or numerals. The raised part of the cam 62 engaging the roller 63 on the lever 46 rotates the numbering device against the tape carried in a guide channel 52, and a toothed stepping pawl 66 advances the discs to the next serial number. An inking roller 55 carried in a yoke pivoted on a shaft 57 is brought into contact with the printing facets by an arm 92 actuated by a lever 89 associated with a cam 87 on the shaft 24. The spaces 69 between the printing facets on the discs are formed with holes arranged to correspond to the code elements of the numerals on the discs, the coded representation of a character or numeral in the printing position being located in a recess 69 angularly displaced by about 120 degrees. The coded recesses are sensed by a frame 77 carrying five spring-biassed pins and moved in four steps across the discs, the pins being associated with bent portions 76 of pivoted selector bars 72 whose ends are individually associated with the five selectors 74 pivoted on a shaft 173 and co-operating with the ends of levers 95 and the cam assembly of the auxiliary transmitter 37. A bail member 171 for restoring the bars 74 to normal position. at the end of the transmission of each of the signals corresponding to the numerals of the message indication is controlled by a pivoted lever 172, held out of operative position by the raised portion of a cam 177 during two-thirds of a revolution of the shaft 24 during which time the bail 171 is controlled by a cam 179 on the main shaft engaging a roller 178 on the lever 174. The magnet 33 initiating the operation of the auxiliary transmitter and numbering device is operated over contacts 120 actuated by a pivoted arm 119 engaged by a cam 118 when a ratchet 113 has been rotated three steps as a result of the transmission of three successive all-spacing signals. The control of the ratchet is effected through a pivoted pawl 109 carried on a member 105 associated with a cam 102. If a code combination includes a marking element, a projection on the end of lever 127 is moved out of engagement with the end of a corresponding lever 124 and a bail 122 extending across the levers 124 moves upwardly to remove the pawl 109 from the ratchet 113. An extension 136 of the pawl 109 engages a ledge 135 on an extension of the lever 117 to remove the holding pawl 116 so that the ratchet returns to normal position. At the end of a number of messages-for example, tena pin 39 on the number disc assembly engages a pivoted bellcrank 41 which closes contacts 43 and connects the auxiliary transmitter 37 to the line. The auxiliary apparatus of the receiver, Fig. 8, is mainly similar to that at the transmitter, the secondary shaft 257 being driven from the main shaft when release lever 329 is operated by a cam 333 as a result of the reception of three successive spacing signals and the energization of magnet 249. operating its armature 289 to allow shaft 323 ‹to rotate. A numerical printing wheel is actuated to print the message number on the tape passing through the guideway 339 and a sensing device is moved across the recesses carrying code projections corresponding to the message-identification number. At the'end of the predetermined number of messages, a pin 252 on one of the discs engages a bell-crank 238 to close contacts 253, whereby signals corresponding to the final serial number printed are derived by a sensing device similar to that at the transmitter and are transmitted from the auxiliary transmitter to a relay arrangement which effects comparison with signals emanating from the distant transmitter and corresponding to the identification number printed at that station. Circuit arrangements. The magnet 32 controlling the transmitter 36 is energized over a circuit including a back contact of relay 263- 277, contacts 284 controlled by key 152 and contacts 286 which are opened if the tape breaks or is exhausted. When three all-spacing signals are transmitted, the cam 113 closes contact 120 and a condenser 258, normally charged by a battery 259, discharges over contacts 101 and a winding 264 of a relay which locks up and at contact 267 completes the circuit for the magnet 33. At the end of the tenth message-i.e. when the pin 39 closes contacts 43-the condenser 258 discharges over winding 263 when a cam 272 effects closure of contacts 269, the relay locking up over contact 274. The magnet 33 is energized over the operated contact 273 and the line 200 is switched over to the auxiliary transmitter 37. The locking circuit of relay 263-277 is broken at contact 183 by cam 181 before the completion of the rotation of the shaft 24, the transmitter 36 is again brought into operation, and the circuit of magnet 33 is maintained by cam 182 on the shaft 24. At the receiving station, Fig. 10, the signals are applied by relay 187 to the magnet 186 of the printer or recorder. In the case of an all-spacing signal, the bail 204 associated with the selector bars 209 is not moved and on operation of a bail 195, for example for the printing operation, a circuit is completed for a counting magnet 203 operating a relay 202 which locks up over contact 213 and transfers the circuit from contacts 196, 198 to a second magnet 221 which is operated by a second all-spacing signal. Magnet 221 locks up and operates a relay 222 which prepares a circuit for relay 232 operated when a third allspacing signal operates cam 227 and closes contacts 225. When operated, relay 232 locks up and discharges a condenser 242 through a relay 351 which effects operation of magnet 249 to operate the anxiliary shaft 257. A code combination comprising a marking condition effects the closure of contacts 206 over which relay 208 operates to break the circuit of one or more of the relay chain 203, 221 and 232. If the pin 252 has rocked the bell-crank 238 so that contacts 253 are closed when the third all-spacing signal has been received, the condenser 242 is discharged through a winding of a relay 193 which locks up and provides a shunt path for the receiving magnet 186 and the back contact of the receiving relay 187 is connected through a contact of relay 193 to a relay 251 which therefore responds to the incoming signals. The magnet 249 which controls the auxiliary shaft 257 is also operated so that the signals from the auxiliary transmitter 294 are applied to the relay 295. The code elements of the message indication at the distant station are applied to armature 293 simultaneously with the control of the armature 296 by the code elements in accordance with the message indication at the receiving station. The armatures fluctuate in unison when there is agreement, but in the case of discrepancy the armatures will be in opposite positions, as indicated in Fig. 10, for some element, the agreement or otherwise being tested by a rotatable disc 306 on the receiver selector shaft which closes contacts 302 at approximately the centre of the received code impulses. If the armatures should be in opposition when contacts 302 are closed, a circuit is completed for relay 303 which locks up over release key 330 and at contact 305 completes the circuit for a lamp 311 and an audible alarm 309. If the tape at the transmitter breaks or becomes exhausted, a rotatable lever 315 engaging the tape releases a pivoted trigger having an arm which engages a cam 318. When the arm moves into a recess on the cam, a pin 317 on the trigger rotates a goose-neck lever 150 to open contact 286 and at the same time to latch a member 155. After the replacement or repair of the tape, the lever 150 and trigger member are restored to normal position by depression of the lever 152. U.S.A. Specification 2,296, 845.is referred to.