Touch Tone fourth-column transaction application [telecom]

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In the 1970s the Bell System developed a Transaction Telephone and support network to provide for things like checking account balance and credit card verification. It developed a series of telephone sets, networks, message switching, software, and testing administration facilities to meet this service.

A series of article describing the service may be found at:

The specific article may be found at:

The telephone sets include a keypad. However, this keypad uses a different type of switch than found on Western Electric Touch Tone pads; rather used on calculator keypads.