Of Operation 2

Master Device
A device in a master-slave system that initiates all transactions and commands (e.g., central controller)

Master-Slave Protocol
Communication system in which all transactions are initiated by a master device and are received and responded to by a slave device

Miscellaneous Series Impedance
The summation of the maximum impedance (500 Hz–10 kHz) of all devices connected in series between two communicating devices; a typical nonintrinsically safe loop will have no miscellaneous series impedance

Modem Modulator/demodulator used to convert HART signals to RS232 signals

Multidrop Network
HART communication system that allows more than two devices to be connected together on a single cable; usually refers to a network with more than one slave device

Multimaster
Multimaster refers to a communication system that has more than one master device. The HART protocol is a simple multimaster system allowing two masters; after receiving a message from a slave device, the master waits for a short time before beginning another transmission, which gives the second master time to initiate a message

Multiplexer
A device that connects to several HART loops and allows communication to and from a host application

Multivariable Instrument
A field device that can measure or calculate more than one process parameter (e.g., flow and temperature)

Network
A series of field and control devices connected together through a communication medium