Which of the following is a device that provides local communication between the datalogger and a
computer?
A.
Controllerless modem
B.
Optical modem
C.
Acoustic modem
D.
Short haul modem
Explanation:
A short haul modem is a device that provides local communication between the datalogger and a
computer with an RS-232 serial port. It transmits data up to 6.5 miles over a four-wire
unconditioned line (two twisted pairs).
Answer option B is incorrect. An optical modem is a device that is used for converting a
computer’s electronic signals into optical signals for transmission over optical fiber. It also converts
optical signals from an optical fiber cable back into electronic signals. It provides higher data
transmission rates because it uses extremely high capacity of the optical fiber cable fortransmitting data.
Answer option C is incorrect. An acoustic modem provides wireless communication under water.
The optimum performance of a wireless acoustic modem system depends upon the speed of
sound, water depth, existence of thermocline zones, ambient noise, and seasonal change.
Answer option A is incorrect. A controllerless modem is a hardware-based modem that does not
have the physical communications port controller circuitry. It is also known as WinModem or
software modem. A controllerless modem is very inexpensive and can easily be upgraded with
new software.