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What is RS232 null modem cable?
A null modem cable is a RS-232 serial cable where the transmit and receive lines are crosslinked. In some cables there are also handshake lines crosslinked. In many situations a straight-through serial cable is used, together with a null modem adapter. The adapter contains the necessary crosslinks between the signals.
Is null modem a crossover cable?
A null modem serial cable (frequently called a crossover cable) is used to connect two DTE devices together without the use of a DCE device in between. For this to happen, the Transmit (TXD) and Receive (RXD) pins on one of the serial connectors are flipped.
Is RS-232 straight through?
The RS-232 specification defines two types of serial devices, DTE and DCE. Depending on the type of device on each end of the line, you either need a straight-through or a null-modem (“crossover”) cable in order to communicate. …
What does null modem mean?
Null Modem. Definition – What does Null Modem mean? A null modem is a specially designed cable that allows a “head-to-head” connection between two nearby serial devices (computers) through their communication ports (RS-232).
What is a null modem cable?
A null modem cable. A null modem cable is a RS-232 serial cable where the transmit and receive lines are crosslinked. In some cables there are also handshake lines crosslinked. In many situations a straight-through serial cable is used, together with a null modem adapter. The adapter contains the necessary crosslinks between the signals.
How long is a RS232 cable?
The RS-232 standard specifies this as 15 metres (50 feet). However this is a conservative figure accounting for high serial speeds over high capacitance cabling, for example using a baud rate of 9600 (a common console speed) over typical Cat 5 cabling, the maximum length increases to 100 – 150 meters (328 – 500 feet).
What is a null wire?
The wire type would be the Null wire (or some other name such as sequence wire) that doesn’t actually pass data but rather only imparts a sequence flow on a set of VIs. This wire would be a semitransparent gray wire which would clearly indicate that there is no data present.