USRobotics V.34 user manual Nonvolatile Memory Nvram

COURIER HIGH SPEED MODEMS

Nonvolatile Memory (NVRAM)

User-programmable random access memory whose data is retained when modem power is turned off. Used in Courier modems to store a user-defined default configuration loaded into random access memory (RAM) at power on.

OFF/ON Hook

Modem operations which are the equivalent of manually lifting a phone receiver (taking it off hook) and replacing it (going on hook).

Online Fallback

Afeature that allows high speed error-control modems to mon- itor line quality and fall back to the next lower speed if line quality degrades. The modems fall forward as line quality improves.

Originate Mode

A state in which the modem transmits at the predefined low fre- quency of the communications channel and receives at the high frequency. The transmit/receive frequencies are the reverse of the called modem which is in Answer mode.

Parallel Transmission

The transfer of data characters using parallel electrical paths for each bit of the character, for example, 8 paths for 8-bit characters. Data is stored in computers in parallel form, but may be converted to serial form for certain operations. See Serial Transmission.

Parity

An error-detection method that checks the validity of a trans- mitted character. Character checking has been surpassed by more reliable and efficient forms of block-checking, including Xmodem-type protocols and the ARQ protocol implemented in Courier modems.

The same type of parity must be used by two communicating computers, or both may omit parity. When parity is used, a parity bit is added to each transmitted character. The bit's value is 0 or 1, to make the total number of 1's in the character even or odd, depending on which type of parity is used.

J-10 Glossary