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  Bell Telephone DTMF Dial
and Phone Schematics

By Mike Morris WA6ILQ
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Western Electric 35-type Station Dials - From Bell System Practices,
Plant Series, Section 501-164-115, Issue 4, June 1968, AT&TCo Standard.

The 35-type dials are TOUCH-TONE® dials having twelve pushbuttons. Ten are used in number-letter calling and two are used to give special service connections.

Each pushbutton operates a different pair of frequency contacts which make coil tap closures for 2 of the 7 output frequencies of the dial. All pushbuttons operate the common switch which reduces sidetone to the receiver (section y-z), opens the transmitter path (section e-v), applies bias voltage to the transistorized oscillator (section w-x), and removes the dc path from the tank coil (section k-u), which starts the oscillator.

Western Electric 2500D Telephone Sets - From Bell System Practices,
Plant Series, Section 502-510-450, Issue 1, June 1967, AT&TCo Standard.

Contact Information:

The author can be contacted at: his-callsign // at // repeater-builder // dot // com.



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This page created Aug 2006

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.