DTMF RECEIVER IC MT8870 TESTERThe circuit is configured in balancedline mode. To reject common-mode noise signals, a balanced differential amplifier input is used. The circuit also provides an excellent bridging interface across a properly terminated telephone line. Transient protection may be achieved by splitting the input resistors and inserting zener diodes (ZD1 and ZD2) to achieve voltage clamping. This allows the transient energy to be dissipated in the resistors and diodes,and limits the maximum voltage that may appear at the inputs.

DTMF RECEIVER IC MT8870 TESTER
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DTMF RECEIVER IC MT8870 TESTER