Automatic Electric Type 51 Dial. 11 Digit

[Fabius]

A search of the forum didn't find any info. What is it? The seller has a bunch of them NOS.

http://tinyurl.com/l4kt4dv

[Phonesrfun]

I belive those dials were used in an industrial control environment, rather than telephony.

Update:
Now that I actually look at the photos in the auction, I see that th contact switch pile-up on the back is definitely for telephony, so now I am puzzled.

[tallguy58]

Hey, that's the rare Spinal Tap dial.

Y'know it goes to "11".

http://vimeo.com/49713035

[Russ Kirk]

From the following web page:
http://www.manufacturediscontinued.com/exhibits/telephones/the-wonderful-world-of-rotary-dials.html

An 11 digit dial made by Automatic Electric. These dials were mostly used in communications equipment for functions like radio channel selecting. They operate like normal dials, the dial digit marked "A" makes 11 pulses.

[Fabius]

From the Manufacture Discontinued website is a picture of one in use.

[unbeldi]

I belive those dials were used in an industrial control environment, rather than telephony.

Update:
Now that I actually look at the photos in the auction, I see that th contact switch pile-up on the back is definitely for telephony, so now I am puzzled.

It seem to me that the contact configuration is a break-make type, or transfer type.  The action contact is in the middle.  Most commonly, AE telephone dials are make-make types, shorting all three ON leads.

I doubt this was actually a No. 51 type dial, but the 11-pulse A model was available as the AK-62 configuration for the No. 51.

The dial case of this dial is constructed differently from the 51.

It should be noted that the 0 position is NOT "10", as in the example quoted here, but is simply "0", so this is a little different.

[poplar1]

This is the back of the dial on Ebay:

[Russ Kirk]

Make-break
Make-make

Can you please clarify these terms? I don't understand fully.
Thanks.

[unbeldi]

A make switch is a switch consisting of two contacts that are closed when the switch is activated.  They are also called normally-open (NO) switches.

A break switch is the opposite, it is normally closed (NC), and when operated breaks the connection.

So, in telephony we often have switches that perform both of these actions at the same time, sometimes on two sets of two contacts, or on a set of three contacts.

The chart below shows switch arrangements on Automatic Electric dials. IIRC, this came from a catalog of the 1930s or 1940s, and didn't change much into the 60s.

Each dial and each diagram have principally two sets of contacts.  Those that provide dial pulse, and those that perform other functions. These latter ones performing other functions than dialing, are also called off-normal (ON) contacts, or as AE labeled them, shunt contacts.

The diagram is a little confusing, actually, because it shows the dial in off-normal position, that is when wound up. So the shunt contacts have been operated, while the pulse contacts have not (yet).

In this diagram you see the type labeled AK-26.  The off-normal contacts consist of three in which the middle one connects to either one or the other contact, but not to both at the same time.  So, therefor, this is a break-make switch.  It breaks one connection and makes another.  It may also be called a transfer switch, which simply means that it has only three contacts total and the signal on the middle contact is transferred from one to other.

This is the type of contact assembly, that I see on this dial.

Referring to the AK-27, as another example, I would call this a break-make-make type. Its normal position connects two leads (the top) and breaks them, in order to connect the action spring to all of the contacts of the pile below.

The dial pulse springs are normally closed in the vast majority of telephone sets.  Only very few private switching systems, PAX, PABX systems, use sets that have normally open dial pulse contacts, such as some Kellogg and Stromberg-Carlson systems. Such phone cannot be used on a normal central office line.

[Russ Kirk]

That explains it completely. Thank you. I'm always learning something here!

[unbeldi]

I just made some corrections in my explanation, because I got confused about the state in which the dials were drawn for the diagram.  They are in the OFF-NORMAL position, not at rest, which I guess would be called the NORMAL position.

The dial found on most AE telephones is the AK-25 type.  It has three contacts that are open when the dial is at rest, and these are shunted when the dial is wound up to the off-normal position until going back to rest.