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Method for Direct Attachment of a Data or Stored Voice Device to a Public Switched Telephone Line

IP.com Disclosure Number: IPCOM000060005D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Hoegh, BT: AUTHOR [+4]

Abstract

A method is described which allows the attachment to the public telephone network of a computer data device or a stored voice device to meet the Federal Communications Commission (FCC) attachment requirements with a minimal amount of hardware circuitry. A direct attachment interface to a telephone line for a data or stored device must perform the following functions: 1) Provide isolation and surge protection that satisfies FCC requirements 2) Couple voice band energy to and from the telephone network. 3) Control the DC current on the network to provide an off-hook indication. 4) Convert a two-wire circuit to a four-wire circuit. 5) Detect the ringing signals from the telephone network. 6) Eliminate excessive levels of transmitted signal. 7) Provide a two-second delay before transmitting data or non- live voice.

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Method for Direct Attachment of a Data or Stored Voice Device to a Public Switched Telephone Line

A method is described which allows the attachment to the public telephone network of a computer data device or a stored voice device to meet the Federal Communications Commission (FCC) attachment requirements with a minimal amount of hardware circuitry. A direct attachment interface to a telephone line for a data or stored device must perform the following functions: 1) Provide isolation and surge protection that satisfies FCC requirements 2) Couple voice band energy to and from the telephone network. 3) Control the DC current on the network to provide an off-hook indication. 4) Convert a two-wire circuit to a four-wire circuit. 5) Detect the ringing signals from the telephone network. 6) Eliminate excessive levels of transmitted signal. 7) Provide a two-second delay before transmitting data or non- live voice. The interface design shown in the figure accomplishes all the above functions. Items 1 through 4 above are satisfied using a traditional "wet transformer" design. Item 5 has been satisfied by using a half-wave current detector B, which then passes pulses to a microprocessor H. Microprocessor H is a software algorithm that determines from the duration and pulse repetition rate whether a valid "Ring In" signal is being received from the telephone network. This design eliminates having to implement in more costly hardware an integrating function to produce a DC l...