Patent GB-191500580-A (GB)
Title: Improvements in Manual and Semi-automatic Telephone Systems.
IPC: H04M5/08
Filed: 1915-01-14
Abstract: 580. Relay Automatic Telephone Co., [formerly Betulander Automatic Telephone Co.], and Aitken, W. Jan. 14. [Cognate Application, 869/15.] Exchange systems.- In systems in which incoming junctions arc provided with means for automatically oonnecting the B-operator's telephone set to the junction, when the A- operator takes it into use, several calling junctions may be indicated by the glowing of their lamps, but only one junction can connect to the operator's telephone at a time. Provision is made for automatic disconnexion of the junction circuits when the A-operator clears. First arrangement. Fig. 1. The relay HR, energized over the junction, completes a circuit 3 for the call lamp CL, and a circuit 4 over a back contact of a common cut-off relav CO for the control relay CR, which (1) connects the operator's spcaking set to the junction over circuit 7, and (2) locks up over circuit 5 and completes a circuit 6 for the common relay CO, both these circuits being dependent on the sleeve relay SR. Having learnt the connexion required, the operator depresses the key K of the calling junction, thereby (1) opening the circuit of the lamp CL, (2) closing a circuit 8, dependent on the relay HR, for the retaining-magnet KC of the key K, and (3) extending the junction to the plug P. After testing the wanted line, the insertion of the plug energizes the sleeve relay SR, which opens the circuits of relays CR, CO so that a call on another junction can be received. When the A-operator disconnects, the relay HR disconnects the magnet KC, thus releasing the key K and giving the clearing-signal to the B-operator. Second arrangement, Fig. 2, in which the incoming junction is not provided with a switch or key of any kind. The relay HR, energized as in the arrangement shown in Fig. 1, completes a circuit 3 for the call lamp CL, and a circuit 4 over a back contact of the common relay CO for the control relay CR, which (1) connects the operator's speaking set to the junction over circuit 7, (2) locks up over circuit 5 and completes a, circuit 6 for the common relay CO, both these circuits being dependent on the sleeve relay SR, and (3) prepares a testing-circllit 9 to the tip of the plug, Assnming that the wanted line is idle, the insertion of the plug energizes a high - resistance relay HS, which closes a circuit for the supervisory lamp SL and energizes the disconnecting-relay DR, which locks up over circuit 16, extends the junction towards the plug, and energizes the sleeve relay SR. This relay opens the circuits 5, 6 of the relays CR, CO so that calls on other junctions can be received, opens the testing-circuit 9, and connects the junction through to the plug P and called line. The ringing-relay RR connects the ringing-current to the called line through a marginal relay TR, which, when the subscriber replies, removes a short-circuit around the ringing-control relay RC, which in turn short-circuits the ringing- relay RR and completes the talking circuit. When the A-operator clears, the relay HR opens the locking - circnit 16 of the disconnecting- relay DR, thus entirely disconnecting the called line. The relay SR remains energized over the contncts of relay HS, which is alone connected to the test circuit. The resistance of the relay HS is so high that its connexion to the test circuit does not mark the line as busy, but the parallel connexion, during a conversation, of the relay SR is sufficient to mark the line as busy. The relay HR also removes the shunt circuit around the clearing-lamp SL, which glows until the operator removes the junction plug, thereby de-energizing the relays HS, SR. Specincation 20,453/14 is referred to The Provisional Specification 580/15 states that the invention is applicable to traffic distributor systems. If, when the B-operator is completing one connexion, two lamps should glow, both lines would be connected automatically to her telephone when the first connexion was completed; to provent the consequent confusion, the operator can disconnect one line by inserting its plug in a special jack with an earthed bush, thus energizing the sleeve relay of this junction.