315,735. Automatic Telephone Manufacturing Co., Ltd., Passmore, W. O., and Taylor, R. April 16, 1928. Semi-automatic exchange systems.-In a system in which a B-operator's keyboard controls the sender storage relays over 4 code wires, circuits are made over certain of these wires, (1) by the cancel key, (2) if the A-operator fails to take the junction by the time the complete numbers has been set up, to cause the release of the sender, (3) after a definite time interval if a complete number is not set up, to start the transmission of a special number for routing the call to an operator if the A-operator has taken the junction, or to release the sender if she has not. In the system described, the operation of an assignment key causes switches JFS, SFS in a link preselected by an alloting switch OFS to hunt for the junction and for an idle sender respectively, and when a sender is found, a relay KR in the link connects the key strip to the code wires, which are switched from one storage group to the next by a group of relays DU - - DM which are cut into the locking circuits of the storage relays in turn when a key is released. Specification 229,765 is referred to in the Provisional Specification. Associating assigned junction with registersender. When the B-operator presses the assignment key ASK of the junction shown, AS pulls - up, locks itself, marks the junction calling and over 207, ST (on OFS), 223, 224 energizes FS in the preselected link. FS completes driving circuits for magnets DM2, DM3 of the switches SFS, JFS over their test wipers P. When SFS finds an idle sender, KS being no longer shortcircuited pulls up, locks itself, grounds wiper P to busy the sender and energize CH, energizes KR and lights L1 in the link and L in the junction. KR connects the digit keys over wipers W - - Z to the 1st storage group MW - - MZ and grounds one end of KJ which if or when JFS has found the junction pulls up, disconnects DM3 and grounds the test wiper to busy the juction and energize JS. JS releases FS, connects the junction wires 204, 205 to the impulsing circuit, holds AS and energizes BG. When the A-operator plugs in, L, LZ, PS pull up, the latter energizing RR. Registering number. The number is now written down on the key strip and stored in the groups MW - - MZ. The storage relays lock up in circuits which become effective when the key is released and include the relays DM - - DU of which DM - - DD switch over the key wires to the next storage group and DU initiates the transmission of impulses, assuming the A- operator has plugged in, by energizing SY over 263, 284, 285, ST. Transmitting number. SY releases KS, KR. KS steps on the allotter OFS and puts out the junction lamp L. KR energizes PY which locks up, extends the out-impulsing wires over wipers X, Y, marks the link busy and, over 27, Z, 215, 247, 286, energizes SS. KR also releases KJ which releases SY, RR, the junction remaining guarded by PY. SS connects the impulse wires 213, 214 to interrupter 91 which is at present short-circuited at 50, and connects interrupter 92 to the sending chain ST - - SG. This comprises 6 two-step relays and is built up to SG by the 1st 6 impulses, each relay releasing the preceding one. SG remains operated while the next 5 impulses re-build the chain to SE. SA on pulling up at the end of the first impulse energizes the pick-up relay SB which partially energizes the first sequence relay CH. Stop relay SZ pulls up when the chain reaches the point marked by the thousands storage group and SB and SZ then fall sluggishly to give hunting time, the relapse of SB allowing CM to operate completely and substitute the hundreds for the thousands marking. The remaining digits are sent in a similar way. Releasing register sender and link. SZ afterthe final digit energizes CO over 212, 288, 302. CO locks up over its upper winding, 72, 208, W, in series with RR (upper), bridges the outgoing trunk, and ungrounds 212 to release the storage and sequence relays. CO also locks over a lower winding and front contact of SZ to prevent premature seizure of the sender. RR unlocks AS, JS, JS unlocks PY, and PY releases CO, RR. CO releases CH to make the sender selectable. Repeating reply and busy signals to A-operator. After the relapse of JS relays I, D which are bridged across the trunk are no longer sbortcircuited and I pulls up and holds BG. When the called party replies, D connects LA to wire 202 of the junction to signal the A-operator. If the subscriber is busy, I, which is short-circuited by the flash impulses, connects LA to 202 intermittently. When the A-operator takes down the cord, L falls back and releases LZ. If I is back, it is re-energized on the relapse of L and holds BG, PS until the end of the flash impulse. Otherwise the relapse of L releases I and BG, PS fall back at once. Cancelling wrong setting. If at any stage before keying the 4th digit, the operator presses CK, circuits are made for the Wand Y relays in the next storage group and these energize CO to release the storage and sequence relays. Routing incompletely set calls to special operator. 4¢ seconds pulses on 306 are connected by KJ to TY when the junction is associated with a sender. When the first pulse goes off, TY extends the pulse wire to SY which, on the next pulse, releases KR and if RR is operated, energizes PY and (over ST (SFS), 285, 284, 316) MB which locks up, and switches over the marking wires 298 - - 301 from the storage relay contacts to the lower side of the frame 1DF, jumpering at which determines the transmission of an appropriate number to route the call to a special operator. The wire 296 which is grounded over 215 is connected to SS (1DF) to initiate the transmission. If it is not desired to route the call to an operator, the wire 295 is connected to CO (I.D.F.) and relay CO releases the sender. Similarly if fewer digits than 4 are necessary the appropriate marking wire is jumpered to CO (I.D.F.). A-operator plugs into the wrong junction or does not plug in. LZ in the wrong junction connects its lamp L to flash impulses at 190. L, LZ, PS in the assigned junction being unoperated, RR in the link is not operated and the energization of SY when the number has been set up energizes CO over 304, W, 208, 209 to restore the sender. If in this case the B-operator failed to set up a complete number, SY, when operated by the time pulse, operates the W and Y relays in the next storage group to operate CO. Control of allotting switch. If a number is not fully set up, KS is not released by SY to move the allotting switch on, but if a new assignment is made, IC which was partly energized when FS fell back pulls up completely when FS is energized for the 2nd time and energizes SY whereupon KS falls and a new link is allotted. If all the senders are busy, SQ energized in a chain circuit by the relays CH in all the senders, lights lamps L<1> in the links and removes ground from the wires such as 317 in each of them. When a link is idle its wire 317 is connected over 341 to the stopping positions of the allotter. Consequently, if all the links or all the senders are busy, the switch is prevented from hunting continuously. Statistical metering; release failure alarm. PY operates a position meter when the transmission of impulses is initiated. RG, which is normally short-circuited by the holding ground, operates an alarm when this ground is removed if any of the relays in the sender fail to unlock.