Roadstar CLT-700, Руководство по обслуживанию

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During the pulse comes out, the CPU makes the Q5 on by maintaining PPD_CON (pin
25 of CPU) high, in this time the switching board will acknowledge the dial clearly by
the occurance of the low impedance.
10. EEPROM
U6 is the EEPROM.
This stores the identification code which are inherent to pair of base unit and handset
to safe guard against interference. It also stores telephone numbers for memory dial.
11. Reset circuit
Reset is applied by connecting an external capacitor C70 and a diode D7.
12. Speech network
R20, R21,C16, C17, and C18 are used for impedance matching between telephone
line and phone.
The resistors and capacitors connectors connected pin10, 16 of U1 are for side tone
balance.