- A History of Engineering and Science in the Bell System: Switching Technology (1925-1975)
Authoritative history of Bell switching including SxS, panel, crossbar and ESS.
- AE 1957 dial equipment catalogue excerpt
Excerpt of AE dial central-office equipment catalogue.
- AE 58466 Test Connector circuit
Drawings for an AE test connector circuit (switch that connects the test desk to subscriber lines).
- AE Bulletin 505: Lubrication of Automatic Switching Equipment
Lubrication points and schedules for Strowger equipment.
- AE Training 800: Elementary Principles of Telephony, part 2
Earlier edition excerpt of AE training 800.
- AE Training Bulletin 800: Electrical Principles of Telephony
First booklet of AE's Strowger training series: electrical basics.
- AE Training Bulletin 801: Mechanical Principles of Telephony
Mechanics of relays and Strowger switches.
- AE Training Bulletin 802: Fundamentals of Apparatus and Trunking
How linefinders, selectors and connectors are trunked together.
- AE Training Bulletin 805: The Plunger Line Switch and Associated Master Switch
Keith plunger line switch and master switch operation.
- AE Training Bulletin 806: The Rotary Line Switch
Rotary line switch (preselector) operation.
- AE Training Bulletin 807: The Connector
AE connector switch operation and circuit; key for a small PBX.
- AE Training Bulletin 808: The Selector
AE selector switch operation and circuit.
- AE Training Bulletin 810: Pulse Repeaters
Pulse repeater operation.
- AE Training Bulletin 812: Power and Supervisory Equipment
Exchange power plant, ringing machines, tones, alarms.
- AE Training Bulletin 813: Party-Line Connectors and Trunk-Hunting Connectors
Connector variants for party lines and hunting groups.
- AE Training Bulletin 815: The Test and Verification Switch Train
Explains AE test distributors, test connectors and verification switches used to test lines and switch trains.
- AE Training Bulletin 818: P-A-X's with P-A-B-X Appendix
Private automatic exchanges and PABXs: the system-level guide for a small home PBX.
- AE Training Bulletin 821: Linefinder Switches
Linefinder switch operation and allotter.
- American Telephone Practice (4th ed.)
Standard reference including the early automatic exchange chapters.
- An Electromechanical Telephone Exchange (PoC||GTFO 21:08)
Hobbyist build of a small exchange from stepping switches, with circuits: a practical model for a small home PBX.
- AT&T Step-by-Step Equipment Engineering Notes, Bulletin 21.5 (part 1)
Early Bell engineering notes on SxS equipment design and trunking.
- Automatic Electric History
Short history of Strowger, Keith and the Automatic Electric company.
- Automatic Electric Standard Adjustments (compilation, 1940s-50s)
933-page compilation of AE adjustment requirements for relays, Strowger switches, line switches, keys and jacks. The core maintenance reference for a working SxS system.
- Automatic Telephone Practice (6th ed.)
Early practical text on automatic (Strowger) telephone systems.
- Automatic Telephone Systems, Vol. 1
British treatise on automatic systems (Strowger) circuits and apparatus.
- Automatic Telephone Systems, Vol. 2: Auxiliary Services and Private and Branch Exchanges
Private and branch exchanges in Strowger practice.
- Automatic Telephone Systems; House Telephones; Testing of Telephone Circuits...
ICS course text with early Strowger exchange description.
- Automatic Telephony: A Comprehensive Treatise on Automatic and Semi-Automatic Systems (2nd ed.)
Classic US text on Strowger/AE and other automatic systems, with circuits.
- Bell Laboratories Record, March 1949 (No. 5 Crossbar)
Introduces the No. 5 crossbar system (context for what replaced SxS).
- Bell System Switching Timeline 1878-1975
One-page timeline of switching systems (image).
- BSP 030-705-701 197- and 198-Type Switches, Requirements and Adjusting Procedures
Bell adjustment requirements for the WE 197-type step-by-step switch (Bell's Strowger).
- BSP 030-705-703 197- and 198-Type Switches, Contact Springs Requirements and Adjusting
Bell spring requirements for 197/198 switches.
- BSP 030-705-802 197- and 198-Type Switches, Piece-Part Replacement
Bell piece-part replacement procedures for 197/198 switches.
- Bulletin 1026: Strowger P-A-X
AE sales bulletin describing the Strowger private automatic exchange.
- Bulletin 1030: Automatic Telephony as a Career
AE recruiting booklet describing the Strowger system and AE factory.
- Catalog 4014: Strowger Dial Telephones and Telephone Parts
AE telephone and parts catalogue.
- Circular 1702-E: Relays and switches for industrial use
AE industrial catalogue of telephone-type relays and stepping switches with specs.
- Design and Performance of Magnets in the Automatic Telephone
Thesis on the electromagnets of Strowger automatic switches.
- E-18898-A-1 Test Distributor Selector Circuit
Early AE circuit explanation for a test distributor selector.
- E-580260 Connector Circuit Explanation (local or toll, trunk/level hunting, night line)
Step-by-step circuit explanation of an AE connector; the textual companion to H-580260.
- E-75159 10-Line Isolated PAX, 24 Volts, circuit explanation
Circuit explanation of a small 10-line AE PAX at 24 V: the closest published analogue to a 3-phone home PBX.
- E-85175 Dial Speed Spotter (pulse testing) circuit explanation
Circuit explanation for AE dial speed/pulse testing circuit; useful for checking dial speed and break ratio.
- E-85289 / AH-85289 Linefinder Test Circuit for Switch Test Stand
Circuit explanation and adjustment for AE's bench test stand that exercises a linefinder out of the shelf; model for bench-testing switches.
- Early Work on Dial Telephone Systems
History of early dial systems including Strowger.
- Evolution of the Strowger Automatic Telephone (chart)
Chart of Strowger telephone/system evolution (image).
- GSP 020-000-000 Tools, Apparatus and Test Equipment: index
Index of GT&E practices on tools and test equipment; finding aid for further 26A-family documents.
- GSP 032-210-108 GTE Automatic Electric Cord Assemblies, Eight or More Conductors
Wiring diagrams and stocklists for AE multi-conductor cords, test plugs (D-57038-A, D-57037-A, D-57163-A) and FD-1003/FD-1006 plugs; likely includes the 26A calling cord (D-543536-A candidate).
- GSP 032-320-702 Test Jack Assemblies and Navy Type Shelf Jacks, Adjustment
Adjustment of switch test jacks and shelf jacks; states the standard Strowger switch shelf jack has up to 24 terminals.
- GSP 108-000-000 Numerical Index, Division 108: Central Office Test Equipment, Portable
Index of GT&E practices on portable CO test equipment; finding aid.
- GSP 230-005-702 Strowger Two-Motion Switches, Wiper Adjustment
Wiper adjustment procedure for AE Strowger two-motion switches (file name follows TCI's number; document header reads 230-005-702).
- GSP 230-010-510 Two-Motion Type Reverting Call Switches, Pulsing Test
Pulsing test procedure for two-motion reverting-call switches.
- H-580156 Selector Circuit, Local and Incoming (issue 6)
AE two-motion selector circuit drawing; directly applicable to wiring a selector stage.
- H-580260 Connector Circuit drawing
AE connector circuit drawing.
- H-85175 Dial Speed Spotter circuit drawing
Circuit drawing companion to E-85175.
- H-856252 Reverting Call Switch, 10-party coded
AE reverting-call switch circuit; the 26A tests these switches.
- H-85919-A Type 26A Switch Tester, Portable Routine Test Set Circuit (sheets 1-2 of 3)
AE circuit drawing for the Type 26A switch tester: full schematic (Fig 1A), remote control set D-322542-A with 15-pin plug, adapter cords, strapping and trip/false-trip tables, key layout. Sheet 3 (calling-cord figures) missing.
- How to Use Rotary Stepping Switches
AE handbook on rotary stepping switches (Type 44/45) and circuits.
- Maintenance Tools, Bulletin 540
AE tool and test-set catalogue; p.24 shows the Switch Tester Type 26 (Portable) H-883635-1 with panel and jack drawings, plus switch test plugs (D-541784-A) and cords.
- Maintenance Tools, Technical Bulletin 150-540 (issue 10)
Later AE maintenance-tool catalogue: Strowger adjusting tools, gauges, test sets and test plugs by H/D part number.
- Maintenance Tools, Technical Bulletin 150-540 (later GT&E issue)
Different issue of TB 150-540 (later GT&E cover); same tool catalogue content, useful for cross-checking part numbers.
- No. 1 Step-by-Step Training Manual, Vol II: Sequence Charts and Operational Sketches
Sequence charts and sketches tracing call progress through Bell No.1 SxS.
- Operating Bulletin 32A1: Installing and Operating Instructions for Type 32A1 P-A-X
Installation and operation of a small AE P-A-X.
- POEEJ July 1936: The Development of 2000 Type Selector Circuits
British GPO 2000-type Strowger selector design and circuits.
- Principles of Automatic Telephony Vol II (Mechanical), Part III: Strowger Switch Construction
Construction of the AE Strowger two-motion switch, part by part.
- Principles of Automatic Telephony Vol II (Mechanical), Part IV: Self-Aligning Plunger Lineswitch
Construction of the AE plunger lineswitch.
- Principles of Automatic Telephony: Circuits and Trunking
AE book on Strowger circuits and trunking.
- Relay Magic
AE promotional booklet on relays (image only).
- Report on the Automatic Telephone Situation in the City of Chicago
Engineering report on the Chicago automatic (AE) telephone system.
- Rotary telephone dials: two families
AE vs WE rotary dial families, pulsing and sound.
- SD-31141 Step-by-Step Systems No.1/350A Test Circuit for station ringers
Bell SxS office test circuit drawing; example of Bell SD/CD format for SxS.
- Step-by-Step Dial System, Pamphlet No. 37
WE installer's introduction to the step-by-step dial system.
- Strowger switch parts catalogue
Late supplier catalogue of Strowger switch spare parts with catalogue and manufacturer numbers.
- SXS Parts Identification Master Drawings (MD)
Exploded master drawings with part numbers for Strowger switch and relay components; essential for repair and ordering parts.
- Technical Bulletin 322: P-A-X/PABX Switchboard Type 50
Type 50 PAX/PABX attendant switchboard.
- Technical Bulletin 405: Test Turret Type 21
AE Type 21 test turret: description and circuits of the exchange test desk used to test lines and switches.
- Technical Bulletin 500-407: Leich Type 40 and Type 80 PABX
Small Leich/AE PABX systems.
- Technical Bulletin 565: General Maintenance of P-A-X's
Routine maintenance of small AE private exchanges.
- Technical Bulletin 961-473: Rotary Stepping Switches
Rotary stepping switch types, adjustment and application.
- Technical Bulletin 961-537: Relays Class B and Class C (Type 57-A and 58-A)
AE Class B relay description and adjustment.
- Telecommunications Switching Principles
Modern switching theory text covering step-by-step, crossbar and stored program control.
- Telephone Communication Systems (1970), Vol 1 Ch. 4: Step-by-Step
Textbook chapter explaining step-by-step systems.
- Telephone Reading Course on Step-by-Step Dial System, Section 1
General description of the SxS dial system for craftsmen.
- Telephone Reading Course on Step-by-Step Dial System, Section 2 (mechanical adjustments)
Mechanical adjustments of SxS central office equipment.
- Telephone Switching Equipment Repairman (Electromechanical), CDC 36251, Vols. 1–5
USAF correspondence course on Strowger step-by-step equipment: relays and the two-motion switch, AE-style line finders and distributors, selectors and connectors relay by relay, power, ringing, maintenance, and the Type 26A switch tester (Vol. 3, ch. 6).
- Telephony, Including Automatic Switching
Textbook covering manual and automatic switching.
- Telephony: A Comprehensive and Detailed Exposition
Large reference including automatic systems.
- The Automatic Telephone
Museum booklet explaining automatic telephony and its history.
- The Early Years of the Strowger System
History of the first Strowger exchanges 1891-1900s.
- The step-by-step telephone switching system: Digit absorbing selectors
Digit absorbing selectors.
- The step-by-step telephone switching system: Handling of toll calls
Toll calls in SxS offices.
- The step-by-step telephone switching system: Overview
Clear modern explanation of SxS for novices and practitioners.
- The step-by-step telephone switching system: Reverting calls
Reverting calls on party lines.
- The step-by-step telephone switching system: The connector switch
Connector operation in detail, with test-stand photo.
- The step-by-step telephone switching system: The line finder switch
Line finder operation in detail.
- The step-by-step telephone switching system: The selector switch
Selector operation in detail.
- The Strowger System (chapter, Beginnings of Automatic Telephony)
Scholarly history of the Strowger system's invention and development.
- The Switching Place (Telecom Information Kit No. 3)
Illustrated introduction to exchange history from manual to Strowger to crossbar.
- TM 11-2111 Tools, Testing Equipment and Common Supplies, Step-by-Step Dial Central Office Equipment
Describes AE-supplied SxS test equipment: current-flow test set, stepping-switch test set (varying machine), test handset with switch test plug, test stand with 24-terminal jack, and the routine test procedures.
- US 1,151,541 Calling Device for Automatic Telephone Exchanges
Later dial (calling device) patent, filed 1903.
- US 1,237,208 Automatic Telephone System
Keith system patent (filed 1908) on selector trunking.
- US 2,562,362 Testing System Employing Test Distributor and Test Connector Switches
AE test distributor/connector system.
- US 2,632,817 Testing Apparatus for Telephone Systems
Telephone test apparatus patent.
- US 3,600,525 Test Set for Strowger Switches
Portable Strowger switch test set design; comparison for the 26A.
- US 447,918 Automatic Telephone-Exchange
Strowger's founding patent.
- US 486,909 Automatic Telephone or Other Electrical Exchange
Strowger's improved exchange patent (vertical-and-rotary switch).
- US 597,062 Calling Device for Telephone Exchanges
The first rotary dial patent.
- US 638,249 Electrical Exchange
Keith/Erickson switch close to the modern step-by-step switch.
- US 815,321 Automatic Telephone Selector Switch
The two-motion selector switch patent.
- Wire Communication Pamphlets 2, 7 and 11 (incl. No. 11 Elements of the Automatic Telephone System)
Bound set; Pamphlet 11 explains the AE private automatic exchange connector circuit step by step.
- Your Strowger Automatic Equipment is tested (advertisement)
One-page AE advertisement on factory testing of Strowger equipment.
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