Dear Elton,

I have a Pittsburg insulator that once belonged to Gerald Brown. Gerald described it in his books as having the marking "FEB 14 PAID". But looking at it again, I noticed that it clearly is marked "FEB 16 PAID". Would this be a new control marking? 
Allen Box

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Dear Allen,

Yes, this deletes the FEB 14 date and adds FEB 16. Jack did make a list of all the datings that were reported. At one time we thought maybe we could decode the year dates if we got sufficient data and relied on a process of elimination, assuming that it would be unusual for the dates to have been applied on Sundays. However, this all seems futile  anyway for several reasons.

First of all, the plant could have been very busy and working Sundays during the war years 1916-18, or even more likely during the boom years after the war.

Secondly, the stamping on trimmed insulators would be applied at the trimming operation, and that is done anywhere from one to several days after the insulators are pressed. On styles not requiring trimming, the date stamping was probably done at the time the items were pressed.

Elton

On the next page is a list of the known Pittsburg date control and full date markings. Many of you may be interested to know if there are other markings that have not been reported. If you have an insulator with a marking not on this list, please drop me a postcard, and we will publish an updated list.

Dear Elton, 

One of my friends showed me a huge sky glaze post insulator that I have never seen before. It is 7" x 15-1/2". The unit has a 3/4" conduit inlet for a three-wire insulated cable leading into the base. Two of the wires have green insulation, and the other is white.

The bottom of the metal base is marked "U.S. PAT. 3251014". On the top there is the number 1301-21 and a logo (above) under-glaze in black ink. It is also marked JAN 1983 on the bottom skirt.
William Ogden NIA #1857

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Dear William,

This insulator is Model #1301-21 which is manufactured by Sigma Instruments, Inc., and is a high voltage current sensor enclosed in a porcelain insulator. The logo is the logo of Fisher Pierce, a Division of Sigma Instruments, Inc., of Braintree, Massachusetts.

The insulator is used in an instrument system to control the power factor of a three phase power line. Hopefully, I can correctly explain how the insulator is used without getting bogged down in the technical jargon.

There is an inductive coupling device (measuring coil) mounted horizontally (parallel to the conductor -- power distribution line) in the upper body of the insulator. A voltage is induced from the high voltage power line (mounted on top of the insulator) without physically tapping into the conductor. This induced voltage from 21 (See Figure 1), in response to the current (amperage) passing through the conductor, is compared to the voltage generated in the secondary winding 14 of transformer 12 using the instrument 18. The instrument either connects or disconnects the capacitor to maintain the proper phase angle -- power factor -- of the high voltage transmission line.