【單選題】In HDLC, frame acknowledgment, flow and error control are the functions of .

【單選題】以下流程圖的基本元素中，表示程序中的輸入輸出框是( )。

【單選題】Two coding schemes, B8ZS and HDB3 are commonly used in long-distance transmission, which are based on the use of .

【填空題】R256是內部“字”繼電器WR25的( )號位。

【多選題】變量必須先定義后使用。定義變量需要確定變量()

【單選題】In ARQ，if a NAK frame is received，only the lost or damaged frame is retransmitted.

【單選題】下列關于局部變量和用戶變量的描述中，錯誤的是()

【多選題】表示邏輯與的運算符有()

【單選題】Delay distortion and attenuation are .

【單選題】E1 carrier link multiplexes channels according to TDM. The original analog voice signal is digitized using PCM at a rate of 8000 samples. So,the data rate of E1 is .

【填空題】The least expensive and most widely used guided transmission medium is

【填空題】填寫完整，表示職稱duty為副教授或教授、年齡age小于40歲的關系表達式：age<40 (duty=="副教授" or duty=="教授")

【單選題】以下程序：a=input("please input a：")if a=="A": print(ord(a))print("OK")運行時輸入：A程序的執行結果是( )。

【填空題】The guided transmission media include twisted pair, coaxial and ( )

【單選題】Full-duplex transmission means two stations can simultaneously send and receive data from each other. This requires .

【單選題】For a noise-free channel with a bandwidth of 3kHz, assuming the possible voltage levels of each symbol signal in the channel is 16, the maximum data transmission rate that the channel can support is ( ).

【單選題】以下程序：x=eval(input())if x%2==0: print(2,end=',')if x%3==0: print(3,end=',')if x%5==0: print(5,end=',')運行時輸入：30程序的執行結果是( )。

【單選題】The procedure is used in HDLC frame to avoid confusion with data containing Flag Fiel bits.

【單選題】2. 下列說法錯誤的是( )

【單選題】 is generally only a minor annoyance for analog signals, but it is the primary source of error in digital data communication.

【單選題】The purpose of twisting for twisted pair is .

【單選題】Which one of the following elements does not affect the data rate of channel.

【單選題】The multiplexing mode ( ) used in CDMA system.

【判斷題】局部變量必須在存儲程序中定義和使用。

【判斷題】運算符+和-可以用來計算日期

【單選題】If the predetermined generation polynomial is P(X) = X4 + X3 + 1, the number of CRC bit derived by this P(X) is ( )

【單選題】MySQL語言中不可使用的邏輯運算符是()

【多選題】用單引號括起來的常量有()

【單選題】14) HDLC is a kind of data link control protocol.

【填空題】R256是內部“字”繼電器()的其中一位。

【多選題】表示邏輯或的運算符有()

【判斷題】In general, the bandwidth is wasted largest in FDM system.

【單選題】In Sliding-Window flow control protocol, the frames located on the left side of the receiver’s window are .

【單選題】A file is transmitted from A to B .The data rate is 9600bit/s .After one hour of continuous transmission, 150 error bits are received by B . What is the bit error ratio(BER) of the channel?

【判斷題】A broad-band data link has higher data propagation volicity than narrow-band link.

【單選題】 is caused by the fact that the velocity of propagation of a signal through a guided medium varies with frequency.

【填空題】關系表達式 "abc" >= "ad"的運算結果是( )。

【判斷題】A telephone channel with a 3000-Hz bandwidth and a signal-to-noise ratio of 20dB, this channel can provided reliable voice transmission with data rate 56kb/s.

【單選題】When the input data streams with different data rates are multiplexed on a TDM link, the various sources is synchronized by technique.

【單選題】結構化程序的三種基本控制結構是()

【單選題】The type of HDLC frame is determined by .

【單選題】下列選項中，不屬于MySQL合法常量的是()’

【多選題】以下表達式結果相同的是()

【填空題】The common multiplexing technique used in communcation system are 、TDM、WDM and CDM.

【單選題】 is the most inefficient error-control mechanism.

【判斷題】5<>5與5!=5結果相同

【單選題】與表達式35%3值相同的表達式是

【單選題】The data rate of the multiplexed line in STDM is .

【單選題】In TDM system，if the data of one channel is error, how to apply error control technique?

【判斷題】case語句能根據不同條件選擇執行不同的語句或語句塊

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