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Antennas, Accessories, Connectors, and Components
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Serial data transmission.

Serial data transmission is the most common method of sending data from one DTE to another. During transmission, the data must pass through a serial interface to exit a computer as serial data. PacketRadio terminal node controllers (TNCees) employ two types of common interface connectors for serial data transfer. These connectors are:

1. DB25
2. DE9 but more often called; the DB9

The RS-232 interface is ideal for the data-transmission up to about 20,000 bits per second, to about fifty (50) feet, or around fifteen (15) meters. RS-232 employs unbalanced signaling and is usually used with DB25 connectors to interconnect data terminal equipment [DTE] (computers, controllers, etc), to data communications equipment [DCE] (terminal node controllers/TNCees modems, etc).

The illustration above, provides a view of the standard RS232 signals as applied to the DB25 connector. Notice that signals/pins 2, 3, 4, 5, and 7, are the most commonly used signals for PC (DTE) to PacketRadio TNCees (DCE).

The 3, CABLES SHOWN BELOW ARE  $14.97 EACH AND ARE SPECIAL ORDERS

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ORDER  CBL  1
This DB25 (DTE) to DB25 (DCE) interface cable is most used between the PC and the AEA/Timewave, Kantronics, and MFJ terminal node controllers.

ORDER  CBL  2
OUR MOST REQUESTED TNC TO PC COMPORT CABLE  $ 14.95
Where the PC utilizes a DB9 comport, the numbering scheme at the PC
end of the cable varies from the wiring scheme of the DB25.

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The late model PacComm and DRSI TNCees employ the DE9 (DB9) comports.

The illustration above provides a view of the wiring scheme for a DB25 DTE to DB9 DCE interface.

Serial data exits through an RS-232 communications port (comport) via the Transmit Data (TxD) lead and arrives at the destination device’s RS-232 comport through its Receive Data (RxD) lead.

To simplify the RS232C signal definitions, I am providing the following RS232C Signal Function Table with Pin Designations relating to both the DE/DB9 and DB25 connectors.

EIA RS232-C Standard