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593 conversion

Started by rdelius, July 23, 2017, 08:34:24 AM

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rdelius

  1957 593 converted to tone dialing.Have not seen another like this.Pad might be a Philips or Norelco

Alex G. Bell

Quote from: rdelius on July 23, 2017, 08:34:24 AM
  1957 593 converted to tone dialing.Have not seen another like this.Pad might be a Philips or Norelco
Correct.  North American Philips AKA Norelco sourced these keypads from a company named Electro-Mech in S. CA and sold them with an oscillator circuit produced in Holland.  They were used in Norelco PAX & PABX systems and sold to telcos for conversion of rotary dial sets. 

The same oscillator circuit was used in Holland with a keypad which used reed switch devices for the matrix and off-normal contacts but it was too deep to fit a 500 set. 

The same Electro-Mech keypad was also used in a DC signaling keypad circuit also used with Norelco PAX and PABX systems.  This latter keypad inserted different resistor values into the line when a key was pressed to encode the digit value.

BTW, the 591 and 593 sets were the 500 equivalents of the 251 and 252 sets: sold to non-Bell companies without ringers for installation of a frequency selective ringer.

rdelius

Circuit board broken, might glue it back and jumper traces. Not worth the trouble. The size  and style of  the keys are similar to a   WE 11 button prototype I have in storage. 11th buttton was DIST.

Alex G. Bell

Quote from: rdelius on July 23, 2017, 03:31:23 PM
Circuit board broken, might glue it back and jumper traces. Not worth the trouble. The size  and style of  the keys are similar to a   WE 11 button prototype I have in storage. 11th buttton was DIST.
The board on the back of the keypad or the oscillator board?

Yes, I also have a WE TT field trial set with large buttons.  In addition it uses entirely different frequencies.  The keypad has plungers and contacts for 12 buttons but the shafts are short and do not reach the back surface of the bezel.  The were made that way (short), not cut off afterwards.

The interesting thing about the Norelco dial and some later digital dials is that it operates directly in the loop ahead of the network although it certainly post-dates Bell Labs' integration of the dial with the network.  It's interesting because it can be used with any speech circuit, not just a 425 or equiv. network.

rdelius

the osc board that plugs into the back of the keypad..I think this set came from and independent telco in PA

Alex G. Bell

Quote from: rdelius on July 23, 2017, 06:06:44 PM
the osc board that plugs into the back of the keypad..I think this set came from and independent telco in PA
A PA indy telco makes a lot of sense.  That was the market.  They advertised in Telephony magazine.

By coincidence, going through a box of misc. TT dials yesterday I happened upon one of these oscillator boards which I married to a standard S-C 35-type keypad with black legends on white keys.  At first I didn't realize it was my work.  I drilled and tapped the metal back of the keypad to mount the board and it looked completely "factory". 

I had not seen one of these in decades.  There must be some cosmic force at work for two to surface so close together.  ;D