Museum of Plugs and Sockets logo, small TAP-A-LINE
outlet with elongated slots
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Tap-A-Line are "Electrical outlets featured by elongated slots and bus-bar connectors to receive closely spaced appliance plugs for such use as in modern kitchens and the like."
They were designed by Robert W. McFarlin and initially manufactured in Milwaukee, Wisconsin. The firm was re-located to Pompano Beach, Florida in the later 1950’s. The design was patented in 1954 (US patent No. 2680233). Images 1, 2 and 5, below, show the original, non earthed model. A version for earthed plugs was patented in 1972 (US patent No. 3668601).
Tap-A-Line never received U/L* approval and production finally ended, possibly in the l980s.
* Underwriters Laboratories, a testing facility and developer of safety standards.

 

Tap-A-Line outlet with elongated slots

Tap-A-Line scheme 1
Tap-A-Line scheme 2
Tap-A-Line logo

Tap-A-Line outlet with plugs

1, 5
Tap-A-Line consists of an extruded plastic strip, that has two brass strips inserted in the extrusion (see image no. 2). Plugs can be inserted into the entire length of the strip. The part of the strip shown that can be used to insert plugs is approximately 24 cm long. Rating, indicated on the label (see image no. 4): 125-250 Volts  12 Amps

With respect to rating the accompanying leaflet states: "How many plugs can be connected to TAP-A-LINE? This depends entirely on the load or wattage consumed. The intent of TAP-A-LINE is not how much you can connect, but how convenient you plug in electrical apparatus." Finally it is concluded that "It is well to remember that the loading on any circuit, depends on the electrical units operating on all the outlets of that circuit, not just one."
2 Drawing that shows how plug pins (flat blades) make contact with live (hot) and neutral brass strips inside the plastic Tap-A-Line housing. The illustration is based in Fig. 3 of patent no. 2680233 (the non-earthed model).
3 Drawing based on Fig. 4 of patent no. 3668601 (earthed model) showing the provisions for earthing. There are a defined number of holes in the plastic housing and corresponding slots in the metal earth contact strip. A 30 cm Tap-A-Line can accommodate a maximum of eight earthed plugs. Note that the outlet is not polarized, also when earthed, 3-pole plugs are used.
4 Tap-A-Line label.

Tap-A-Line leaflet (partial)

Node 12050 outlet with elongated slots

6
Part of the information leaflet that came with each Tap-A-Line. Among others it gives a long list of useful applications. It lists most of the electrical equipment that could be found in 1960s-70s homes, offices, workshops, studios, farms, factories, construction sites and research laboratories.

7
McFarlin's electric convenience outlet with continuous slot has inspired other people to design comparable outlets. One of them is the Node 12050 Electrical Outlet, a relatively new type of wall outlet by Metaphys (Osaka, Japan). An interesting concept, but it seems questionable whether it ever will be approved and produced.

 


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