|2||Transmit||TXD, data transmitted from the densitometer|
|3||Receive||RXD, data received by the densitometer|
|5||CTS||Clear to Send, controls output from densitometer|
|20||DTR||Data Terminal Ready, controls input to densitometer|
Note: Lines 4 and 5 are internally connected.
In general terms, connection of these instruments to IBM compatible computers is via a NULL-MODEM type interface. In NULL-MODEM interfaces, several pairs of wires are crossed so that the receive line of one device is attached to the transmit line of the other. Handshake lines too must be crossed if hardware flow control is to be initiated.