| Pin | Function | Description | Circuit EIA |
|---|---|---|---|
| 1 | unused | ||
| 2 | Digit Present | A signal given to the ACE indicating that the digit lines contain a digit | DPR |
| 3 | Abandon Call and Retry | An indicator signal from the ACE that it could not make a connection. Could be "busy". | ACR |
| 4 | Call Request | A signal from the DTE that tells the ACE to go "off hook" | CRQ |
| 5 | Present Next Digit | A signal from the ACE to the DTE to indicate that the ACE is ready to receive the next digit. | PND |
| 6 | unused | ||
| 7 | unused | ||
| 8 | unused | ||
| 9 | unused | ||
| 10 | unused | ||
| 11 | unused | ||
| 12 | unused | ||
| 13 | Distant Station Connected | Indicator from ACE to DTE that the call is succesfully made. | DSC |
| 14-17 | Digit Signal Circuits | Four lines containing a parallel BCD dial digit (10 digits, plus control digits) | NB1-NB8 |
| 18 | unused | ||
| 19 | unused | ||
| 20 | unused | ||
| 21 | unused | ||
| 22 | Data Line Occupied | An indicator that is used by the ACE to let the DTE know that the line it wants to use is used by another device. | DLO |
| 23 | unused | ||
| 24 | unused | ||
| 25 | unused | ||
correct
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