Patent GB-718255-A (GB)
Title: Improvements in or relating to automatic telephone systems
IPC: C07D213/82
Filed: 1952-12-17
Abstract: 718,255. Automatic exchange systems. TELEFONAKTIEBOLAGETL.M ERICSSON. Dec. 17, 1952, [Dec. 17, 1951], No. 32022/52. Class 40 (4). An originating subscriber on ascertaining that a wanted subscriber is busy may obtain access to a "waiting device" which records the identity of the originating and wanted parties, and connects itself to the link which is at the moment connected to the wanted subscriber. When the link is released the waiting device sets up a connection both to the originating and wanted parties, and if the originating party is free connects them together. If the originating party is engaged in another call the waiting device connects itself to the link over which that call is being made and injects a warning tone. Normal call-The loop from the originating subscriber Al operates the line relay LR1, provided no other line relays of this particular tens group are operated at this moment. The line relay is then held in series with the select magnet S11, appropriate to the tens group concerned, of the register selecting switch RS. Magnet S11 operates chain relay HR1 associated with the first free register in series with RR4 in that register. Relay RR4 brings up hold magnet GR1 in series with RR1 in the register, the former connecting the subscriber to the register and the latter busying the register. Relay T11 operates in parallel with GR1, releases S11, and prevents other line relays of the tens group operating at this time. In the register, impulse relay RR1 operates, followed by holding relay RR3 which connects up dial tone. RR4 releases. The dialled digits are received at OR, which sets the digit registers RM1, RM2; BR1 operating after the first digit is received to disconnect dial tone. After the reception of the second digit BR2 operates the chain relay KR1 associated with the register if the marker M is free. Relay KR1 initiates the slow release of RR3 and operates the chain relay NR9, and the select magnet S9 associated with the first free link SN. The digits registered in REG are transferred to the marker relays U10 ... U90, U1 ... U0, which mark the called subscriber A2. If the called subscriber is free, the test relay MR1 operates in series with the hold magnet B2, and short circuits its high resistance windings thereby bring- ing up B2. MR also completes a circuit over lead r3 for identification relay P11 which causes the identity of the originating subscriber to be transmitted over leads t10 ... t90, t1 ... t0 to the marker relays M 10 ... M90, M1 ... M0, which thereupon bring up the hold magnet B1 of the originating subscriber. The originating and called subscribers are now connected to the same side of the link SN. RR3 releases the marker, the register and NR9 and S9. In the link circuit N2 and N3 operate in series with the originating subscriber's line relay LR1. Ringing current is transmitted over the a, b loop to A2 (LR2 down) and ringing tone over the a-wire to A1 (LR1 up). Relay N1 operates to the called subscriber's answering loop and releases LR1 and N2. Talking battery is supplied over N3 which holds N1, the latter holding Bl and B2. If the called party is busy MR1 fails to operate and a slowto-operate relay MR2 eventually operates to bring up select magnet SO and hold magnet Bl to connect A to a source of busy tone Sul. RR3 releases the register and marker as before. Operation of "waiting" device. Setting the device.- On receipt of busy tone the subscriber Al hangs up and initiates a fresh call, dialling the digit 0, followed on the reception of further dial tone by the wanted party's number. Relay BR2 operates immediately to bring up KR1 which seizes a free link SN as previously described by operating chain relay NR9 and select magnet S9. Relay NR9 also brings up magnet S29 of the waiting device associating switch. The register applies seizing potential to relay chain U91, U92 and relay U91 associated with the first free waiting device V operates in series with relay V3 in the device. Relay U91 operates relay NIR1 which brings up P11 in the identifier P; so causing the marker relays M10 .. M90, M1 ... M0 to mark the originating line, whereupon hold magnet B1 operates to connect subscriber Al to the link circuit SN, LR1, N2 and N3 then operating as before. In the waiting device V3 operates V2 to connect the identifying wires t10 ... t90, tl ... t0 to the register RV10 ... RV90, RVI ... RV0, which thereupon records the identity of the originating subscriber. Relay V3 also operates hold magnet VB1 which thus associates the waiting device V with the link SN. Relay N, in the link is thereby operated and releases LRI and N2. In the waiting device, impulse relay V4 operates over the calling subscriber's loop and brings up V5 which reverts dial tone. The register and marker release as before, de-energizing V3 which releases V2. The wanted number is repeated by V4 to the device VR, which causes the digits to be registered on contact sets VM3, VM4. When the digits have been received, VB4 brings up V8 in series with its associated chain relay KR6 if the marker is free. KR6 seizes a free link similar to SN. Relay V8 causes the registered digits to set the marker and the called subscriber is tested again. Since it is still busy, however, MR2 comes up as before and releases the link seized by KR6. Assuming that the wanted subscriber is busied by being connected to link SN, relay MR3 and magnet S29 are operated over a circuit including the c-wire of the link and the marking wire for the wanted subscriber by an auxiliary battery W in the marker. Relay MR3 brings up V12 followed by V6 and VB2. The latter connects the waiting device V to that link SN which is connected to the wanted subscriber A2. When V6 releases the marker, V8 and V12 fall back. When the originating subscriber A1 hangs up, V4 and V5 release, followed by VB1 and the link circuit over which the subscriber Al made the call is released. Busy wanted subscriber becomes free. When A2 hangs up N1 and N3 fall back and V7 in the waiting device operates in series with the lower winding of N3, which latter however, does not operate. Relay V7 releases V6 and VB2 and the link SN is released. Release of V6 calls in the marker again, if free, by the operation of V8 and KR6. A free link such as SN is again seized by the operation of NR9, S9, S29. The relays UO ... U90 are set by the contact sets VM3, VM4 to mark the called line. The test relay MR1 operates since the called subscriber is now free and operates the hold magnet B2 and relay V9 to bring up hold magnet VB2. Busy potential is applied thereby over rectifier R2 and relay N4 to the c-wire to mark A2 busy. Relay N4 operates. Relay V9 releases V7 and V8. Calling originating subscriber. When V8 releases, the marker is called in by the operation of V2 and KR6 in series. The former transfers the originating subscriber's identity to the marker relays M0 ... M90. The latter seizes a free link causing the operation of, say, NRI, S1, S21. The test relay MR1 operates if the originating subscriber is free and operates B1 to connect the originating subscriber to the seized link. MR1 brings up V10 in the waiting device which operates hold magnet VB1 to connect the waiting device to the link associated with S21. V10 releases V2 and KR6. Relay N4 in the last-mentioned link operates in the holding circuit of Bl. The originating subscriber is now rung from this link over a circuit including an h contact of switch VM1. Originating subscriber answers. N3 and N1 operate to the line loop and V4 operates in parallel with the lower winding of N3. V5 follows V4 and brings up V13 in series with N3 in the link SN associated with NR9. V10 starts a time switch Z which releases the waiting device after a prescribed time. The wanted subscriber A2 is rung from the link SN and when he replies NI comes up in that link and releases V13 which brings up V2, V11 and KR6 in series. Relay V11 causes the release of V10, V6, VB1 and VB2. The holding circuit for BI and B2 are thereby broken and the subscribers released, but they cannot initiate a new call as the lead m4 is broken by KR6. Impulse relay V4 and hold relay V5 release and during the release time of the latter the connection is set up as follows:-Release of V6 connects V8 and KR6 in series, and a free link is seized as before. V2 and V11operate in parallel with V8. With V2 and V8 passing the identities of the originating and wanted subscriber to the marker, a connection between these two subscribers is established, N1 and N3 operating to the subscribers' loops in a circuit including contact 297 of NR9. Release of V5 releases the waiting device and the marker. Originating subscriber busy. When this subscriber is tested, MR1 fails to operate and when MR2 eventually operates MR3 and the magnet S28 (say) associated with the link connected to the originating subscriber Al operate to the auxiliary battery W as previously described. Relay MR3 operates V1 which is followed by V10, so that the hold magnet VB1 comes up thereby connecting the waiting device V to the link connected to A1. V4 comes up to the originating subscriber's loop and is followed by V5, which injects tone into the said loop via relay V4. After a prescribed interval the time switch Z operates V11 which releases the waiting device.