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Ae Type 26a Switch Tester · Volume 1

What It Is

Figure 1 — My GTE Automatic Electric Type 26A Switch Tester with its lid off. On the sloping top panel: the rotary dial, a row of twelve lever keys, two turn keys, the coloured lamps, and red and black bindin…
Figure 1 — My GTE Automatic Electric Type 26A Switch Tester with its lid off. On the sloping top panel: the rotary dial, a row of twelve lever keys, two turn keys, the coloured lamps, and red and black binding posts. The lid carries a document pocket for the circuit drawing and test cords. — My photograph

1.1 A Connector Tester in a Box

The Type 26A is Automatic Electric’s portable routine test set for step-by-step switches, above all for connectors, the final switches of the switch train that find, test, ring and feed the called line (see the Telephone Switching History dive, Volumes 4 and 5). Its circuit drawing describes it in one long title: “Type 26A Switch Tester, Portable Routine Test Set Ckt. for Testing Local, Toll and Comb. Conn., Toll Trans. Sws., Pay Station Repeaters, Rev. Call Sws.” That is: local, toll and combination connectors; toll transmission selectors; pay-station repeaters; and reverting-call switches.

A maintainer carried it to a connector shelf, plugged a calling cord into the connector’s test jack, and plugged an answer cord into the shelf’s test jacks. The tester could then seize the connector, dial it to the shelf’s own test line over a deliberately bad loop, make the test line busy or answer it, and prove each of the connector’s jobs in turn: stepping, busy test, ringing, ringback, ring trip, talking and release. A bad connector shows exactly which job it fails.

The Type 26A could do one thing that a test handset could not: it measures the connector’s ring-trip relay against standard resistances, proving that it ignores a leaky line and trips on a real answer. The US Air Force course Telephone Switching Equipment Repairman (Electromechanical) uses exactly that case as an example. When a customer reports a ring-trip fault that a test handset cannot reproduce, the next step is to “test the connector using the type 26A switch tester” (USAF CDC 36251, Vol. 3, review exercise 75).

1.2 My Unit

Figure 2 — The red nameplate on the front of my tester: GTE AUTOMATIC ELECTRIC, NORTHLAKE, ILL., U.S.A. — TEST SET TYPE 26A SWITCH TESTER — CKT-H-85919-A — PART NO-H-885068-1. The 15-pin REMOTE receptacle is …
Figure 2 — The red nameplate on the front of my tester: GTE AUTOMATIC ELECTRIC, NORTHLAKE, ILL., U.S.A. — TEST SET TYPE 26A SWITCH TESTER — CKT-H-85919-A — PART NO-H-885068-1. The 15-pin REMOTE receptacle is at the left, and the 10-pin receptacle at the right is the VM (pulsing test set) connection. — My photograph

My Type 26A’s nameplate reads:

GTE AUTOMATIC ELECTRIC — NORTHLAKE, ILL., U.S.A. TEST SET — TYPE 26A — SWITCH TESTER CKT-H-85919-A — PART NO-H-885068-1

CKT-H-85919-A is the circuit drawing number, and the drawing itself survives (below). H-885068-1 is the part number of the complete test set. It is housed in a grey hammer-finish steel case with a lift-off lid with draw latches, a carrying handle on top and grab handles at the sides. The top panel slopes toward the user. The front carries the two multi-pin receptacles, four jacks at each side, and the nameplate.

I don’t have its cords. Without the calling cord, the answer cord and the remote control set, it cannot be connected to anything, so Volume 4 is about identifying and making them.

Figure 3 — The front of my tester with the lid on: four jacks at each side, the REMOTE receptacle and the 10-pin receptacle, and the nameplate below the handle.
Figure 3 — The front of my tester with the lid on: four jacks at each side, the REMOTE receptacle and the 10-pin receptacle, and the nameplate below the handle. — My photograph

1.3 When It Was Made

Three facts bracket the date.

  • The circuit drawing H-85919-A was drawn on 20 September 1962 by Automatic Electric Laboratories and approved on 26 September 1962. It went through fourteen issues, the last dated about 1970.
  • “Northlake, Ill.” Automatic Electric moved from Chicago’s West Side to Northlake in 1957.
  • “GTE Automatic Electric.” The parent company adopted the short “GTE” identity in 1971, and Automatic Electric’s own technical journal changed its title to GTE Automatic Electric Technical Journal with the January 1971 issue. The name disappeared when Automatic Electric was merged into GTE Network Systems in 1983 (sources in the history dive, Volume 2).

So my nameplate most likely dates the set to the 1970s or early 1980s. That is an inference from the company’s naming, not a documented rule for when nameplates changed.

1.4 The Type 26 and the Type 26A

Automatic Electric’s 1960 maintenance-tools catalogue, Bulletin 540, lists the predecessor: “Switch Tester, Type 26 (Portable) — H-883635-1 … For general switch testing use,” with drawings of the case (one foot wide), the controls and indicators, and the jacks. Its panel drawing already shows the dial, the RC-VM jack, the START turn key, the lamp row and the same row of twelve lever keys as the 26A, and its jack view puts REMOTE at the left of the front, VM at the right, TRANS and REC among the jacks at one side and four numbered jacks at the other. The 26A’s drawing is dated two years after the catalogue; its part number, H-885068-1, is different from the Type 26’s H-883635-1. No catalogue entry for the 26A itself was found.

Figure 4 — Automatic Electric's catalogue entry for the Type 26 Switch Tester (portable), H-883635-1, in Bulletin 540 (1960), p. 24: side view, the controls and indicators, and the jacks. The 26A that followe…
Figure 4 — Automatic Electric's catalogue entry for the Type 26 Switch Tester (portable), H-883635-1, in Bulletin 540 (1960), p. 24: side view, the controls and indicators, and the jacks. The 26A that followed has the same layout. The jack view shows REMOTE and VM receptacles and four jacks at each side, as on my unit. — Automatic Electric, Bulletin 540, Maintenance Tools (1960), TCI Library via the Internet Archive

1.5 The Documents

Table 1 — The Documents

DocumentWhat it isStatus
H-85919-A, sheets 1 and 2 of 3The circuit drawing: Fig. 1A (the test set), Fig. 3A (the remote control set), Fig. 19A (adapter cords), Fig. AA (typical exchange connections), Table AB (trip values), the key layout and engineering notes 51–67Found, from the Telephone Collectors International (TCI) library, contributed by Paul Wills. In the Reference Library.
H-85919-A, sheet 3 of 3Probably the remaining sub-figures, possibly the Figure B calling cord of note 52. Note 66 says Figs. 15A, 16A and 17A (formerly A, C and D) are provided with the test set, so the note-51 calling cord is Fig. 15A; note 67 makes Fig. 18A the hand test telephone adapter cordMissing from the scan
E-85919-A, issue 3”Explanation”: the circuit description, the nearest thing to an instruction manual. Note 58 refers to it twice for testing procedures.Not found
AH-85919-A, issue 6”Adjustment”: relay adjustment requirementsNot found
AE Bulletin 540 (1960), p. 24Catalogue entry for the Type 26In the Reference Library
USAF CDC 36251, Vol. 3, ch. 6, pp. 72–74Description of the Type 26A, its cords and the test proceduresIn the Reference Library (ERIC ED194781)
GSP 032-210-108 (1972)GTE Automatic Electric cord assemblies of eight or more conductors, with wiring diagramsIn the Reference Library
GSP 032-320-702 (1967)Test jack assemblies and shelf jacks: adjustmentIn the Reference Library

The TCI library was down for maintenance while this dive was researched. Its Automatic Electric “E and H reference documents” folder is the most likely home of the missing sheet and the E-85919 explanation, and Paul Wills, who contributed the drawing, may have them.

Figure 5 — My tester closed up for carrying: the lid latched, the rubber feet on the end that let it stand on end.
Figure 5 — My tester closed up for carrying: the lid latched, the rubber feet on the end that let it stand on end. — My photograph

1.6 In the Reference Library

Sources