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| Levels of Implementation | |
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| Table | ||
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| Pin | Signal | Signal Name and Description |
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| Number | Mnemonic |
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| 22 | RI | RING INDICATOR. Output from the modem to the terminal; |
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| indicates to the terminal that an incoming call is present. The |
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| terminal causes the modem to answer the phone by carrying |
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| DTR true while RI is active. |
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| 23 |
| Not used. |
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| 24 | TxC | TRANSMIT CLOCK (DTE). Input to modem from terminal; |
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| same function as TxC on pin 15. |
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| 25 | BSY | BUSY. Input to modem from terminal. A positive EIA signal |
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| applied to this pin causes the modem to go |
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| the associated phone busy. |
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Levels of Implementation
There are several levels of conformance that may be appropriate for typical
❏Automatic dialing
❏Automatic answering
❏Synchronous transmission
A
E |