TELEPHONE INTERFACE MODULE (TIM)

oscillator of U211 running at ≈ 3.7 kHz. With U244, pin 12 low the output of U210, pin 9 is a “1” (U210, pin 12 is constantly being retriggered). If a transient “0” during a logic “1” is encountered at the E-Lead, U210, pin 7 is retriggered causing U211, pin 3 to go

high for 5 ms. This will not change the output of U211, pin 9 because it is being retriggered. If U211, pin 3 stays high longer than 10 ms, U211, pin 9 goes low. For this to occur, the transient would need to exceed 10 ms.

Figure 14-13 4-WIRE E&M BLOCK DIAGRAM (-680)

14-9