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RED + BLUE TOUCH TONE TELEPHONES
BELL / AT&T MODELS 2500
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T O U C H T O N E PHONE Bell/WesternElectric / USA (1965)
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T H E R E D T E L E P H O N E Model 2500
The debut of the "RED TELEPHONE" was in the 60/70s "Cold-War's
Hot-Line" to the Kremlin. This was the 1st step into the
"Electronic Age": Only 1 ( one! ) transistor and lots of
mechanics - as can be seen in the picture of the keyboard,
taken on a mirror ...
Column Frequencies (Hz) DUAL-TONE - MULTI-FREQUENCY
1209 1336 1477 ( DTMF )
+-----+-----+-----+
| | ABC | DEF |
| 1 | 2 | 3 | 697
+-----+-----+-----+
| GHI | JKL | MNO |
| 4 | 5 | 6 | 770
+-----+-----+-----+
| PRS | TUV | WXY |
| 7 | 8 | 9 | 852
+-----+-----+-----+
| |OPRTR| |
| * | 0 | # | 941
+-----+-----+-----+
Row Frequencies (Hz)
The LETTERS ON THE DIALER are for MEMORIZING TELEPHONE NUMBERS...
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1 4 = G H I 7 = P R S 0 = Operator
2 = A B C 5 = J K L 8 = T U V
3 = D E F 6 = M N O 9 = W X Y
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EXAMPLE: A-T-L-A-N-T-I-S = 28526847 ===>>> »ATLANTIS« Hotel
Historical Remarks ...
R E M A R K T O R E S T O R A T I O N :
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If you got a touch tone telephone and all is working well ( bell,
communication ) except the KEYBOARD doesn't react, than TRY THIS:
The keyboard is sensitive to the polarity of the incomming wires.
Exchange the wires ( RED, GREEN ) either in the outlet or in the
telephone, or use a "crossed" cable between telephone & outlet.
I T M A Y B E N O T N E C E S S A R Y ...
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T O U C H T O N E PHONE AT&T/WesternElectric / USA (1982)
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T H E B L U E T E L E P H O N E Model R 2500 MG
has a GRAETZ-BRIDGE ( Part = 840364202 / 9-82 ) implemented ...
Known from power units ( AC/DC-Conversion ): Independent of the
polarity on Input-Pins 2/3, the Output 4/1 is always ( +/- ).