1. Strowger final selector – idle state _ + A 200 200 CD2 B4 P A1 N3 N2 B2 B 1300 TO F, H AND J RELAYS MR2 CD1 E 1500 METER PULSE CONNECTION HERE NR2 CD R2 200 5 700 F6 E5 B1 R3 1k2 ROTARY RELEASE CONNECTION CD4 E3 H5 NR1 RM VM E1//D1

2. Strowger final selector – moment of seizure – A operates and removes short-circuit of B _ + A 200 200 CD2 B4 A1 P N3 N2 B2 B 1300 MR2 CD1 E NR2 1500 CD R2 5 700 F6 E5 B1 R3 CD4 E3 H5 NR1 RM VM E1

3. Strowger final selector – just after seizure – A, B and CD operate _ + A CD2 200 200 B4 A1 P N3 N2 B2 B 1300 MR2 INCOMING PRIVATE WIRE EARTHED CD1 E NR2 1500 CD R2 5 700 F6 E5 B1 R3 CD4 E3 H5 NR1 RM VM E1

4. Strowger final selector – vertical stepping – A and VM are pulsing, B and CD are holding _ + A CD2 200 200 B4 A1 P N3 N2 B2 B 1300 short- circuit MR2 CD1 E NR2 1500 CD R2 5 700 F6 E5 B1 R3 1k2 CD4 E3 H5 NR1 RM VM E1

5. Strowger final selector – end of vertical stepping – A and B operate, CD releases, E slow to operate _ + A CD2 200 200 B4 A1 P N3 N2 B2 B 1300 MR2 CD1 E NR2 1500 CD R2 5 700 F6 E5 B1 R3 CD4 E3 H5 NR1 RM VM E1

6. Strowger final selector – switch over to rotary – A, B and E operate, CD re-operates _ + A CD2 200 200 B4 A1 P N3 N2 B2 B 1300 MR2 CD1 E NR2 1500 CD R2 5 700 F6 E5 B1 short-circuit on CD removed R3 CD4 E3 H5 NR1 RM VM E1

7. Strowger final selector – rotary stepping – A and RM pulsing, B, CD and E operate _ + A CD2 200 200 B4 A1 P N3 N2 B2 B 1300 MR2 CD1 E NR2 1500 CD R2 5 700 F6 E5 B1 R3 1k2 CD4 E3 H5 NR1 RM VM E1

8. Strowger final selector – end of rotary steps – A and B operate, CD and E release slowly, CD re-operates _ + A CD2 200 200 B4 A1 P N3 N2 B2 B 1300 MR2 CD1 E 1500 R2 NR2 CD 5 700 F6 E5 B1 R3 CD4 E3 H5 NR1 RM VM E1

9. Strowger final selector – called subscriber’s uniselector interface – idle state M.D.F. P K3 B3 MULT. LOCAL P H L1x CD3 K 1300 H K5 DMdm FINAL SELECTOR DM L 700 _ _ H3 K1 + + H4 K2 LINE SIDE M.D.F. SUBSCRIBER’S UNISELECTOR EXCH SIDE

10. Strowger final selector – incoming call – CD releases, H (900 Ohm) and K operate, L is disconnected L2 M.D.F. P K3 B3 MULT. LOCAL 900 P H L1x CD3 K 1300 H K5 DMdm FINAL SELECTOR DM L 700 _ _ H3 K1 PREPARED FOR RINGING + + H4 K2 M.D.F. CALLED SUBSCRIBER’S UNISELECTOR LINE SIDE EXCH SIDE IF NOT ENGAGED

11. Strowger final selector – ringing a free line – E releases slowly, CD, J and H (on 400 Ohm winding) operate F7 H3 _ F8 H4 + A 200 570 200 F2 F1 R1 D H2 CD4 P J3 J1 E RING RTN BATTERY HOLDING UNISELECTOR K RELAY D1 F5 H1 F4x VM N2 F 300 400 RING TONE E4 B4 J 800 H 400 900 RING TONE B3 CD3

12. Strowger final selector – call answered – CD, D, E and F operate, J releases (slowly) after meter pulse F7 H3 _ VOICE CONNECTION F8 H4 + A 200 570 200 F2 F1 R1 D H2 CD4 P J3 J1 E HOLDING UNISELECTOR K RELAY D1 F5 H1 F4x VM N2 F 300 400 RING TONE E4 B4 J 800 H 400 900 RING TONE B3 CD3

13. The end