A test of the internal circuits of two modems and a telephone link between them by which an operator at one modem causes a test pattern to be transmitted to the other modem which, in turn, decodes it, re-encodes it, and retransmits it back to the testing modem.; 兩個調(diào)制解調(diào)器和一個電話鏈路之間的一種內(nèi)部電路測試,操作員在其中一個調(diào)制解調(diào)器 產(chǎn)生測試圖型,傳送到另一個調(diào)制解調(diào)器,依次將它解碼,然后重新編碼,并發(fā)回測試調(diào)制解調(diào) 器。參閱end-to-end test。