在图4-1所示的系统中，R1、R2、R3为3个加工部件，每个加工部件的失效率均为λ，可靠性均为尺。则该系统的可靠性为(4)。若每个加工部件的平均无故障时间为5000小时，则该系统的平均无故障时间为(5)小时。

(159)

(158)

(157)

For each blank, choose the best answer from the four choices and write down on the answer sheet.

(71)is a one-way function that takes an arbitrarily long piece of plaintext and from it computes a fixed-length bit string.

(72)is a protocol that most USENET machines now use it to allow news articles to propagate from one machine to another over a reliable connection.

(73)is an approach preferred by cable TV providers. In this solution the fiber terminates at an optoelectrical converter and the final segment is a shared coaxial cable.

(74)is a device used to connect two separate network that use different communication protocol.

(75)is a digital-to-digital polar encoding method in which the signal level is always either positive or negative.

(156)

(153)

(154)

(152)

帧中继网的虚电路建立在()

(151)