|Trade Name:||Exchange Line|
|Size:||2 1/2" W x 3 1/4" H|
|Production Date:||1914 - 1950's|
|"The use of twisted pairs of wires instead
of two drop-wires require a special insulator, and in 1914, the Hemingray No. 10 pony
insulator was developed for this purpose."
"It is today accepted as standard for most telephone exchange systems. Its grooves are close together to accommodate the twisted pair of wires, and are square so as to hold both wires securely. Somewhat thicker glass sections make it much sturdier than early exchange system types."
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