outlet with elongated slots
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.
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
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."
that shows how plug pins (flat blades) make contact with live (hot) and
neutral brass strips inside the plastic Tap-A-Line housing. The
is based in Fig. 3 of patent no. 2680233 (the non-earthed model).
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.
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.
McFarlin's electric convenience outlet with continuous slot has inspired other people to design comparable outlets. One of them is the Node 12050 Outlet designed by Metaphys (Osaka, Japan). An interesting concept, but it seems questionable whether it ever will be approved and produced.
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