Roadstar CLT-700, Руководство по обслуживанию

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Speech network adjusts a transmit signal gain and sends it to the telephone line
through switching transistor Q3, bridge diode (D1, D2, D3 and D4) and modular jack
JP1.
5. Sending and Receiving of data signal
The sending MSK data comes out from TX_DATA of CPU (pin 43), and enters into pin
4 of U10 (compander).
It is modulated at RF block through the same path as audio signal.
The received MSK data which demodulated at RF block with the same manner as
audio signal is going to the low path filter composed of U8C, C47, C48, C49, R64, R65
and R67. Filtered signal is comparated at U8D. The square wave from U8D(RX_DATA)
is fed to pin 44 of CPU.
6. Ring detector circuit
When the ring signal is supplied to U2(photo coupler) through C1, R1, DZ1, DZ2 and
R3, U2 detects it and send a RING_SIGNAL signal to pin 31 of U4 (CPU).
Then the base unit sends a ringing data through the "sending data path" to the
handset.
7. Line detect circuit
If the telephone line is connected, the Q2 will be on, LINE_DETECT signal become low
level. Then CPU knows that tel-line is connected.
If the telephone line is not connected or higher priority telephone is operated, the Q2
will be off and CPU knows that tel-line is not connected or higher priority telephone is
operating.
This function is factory settable option.
8. DTMF signal
In case that the phone is in tone dialing mode, it is possible to use DTMF dial.
DTMF signal is generated by U3 by the command of D0, D1, D2 and D3 from CPU
(pin 11, 12, 13, and 14).
DTMF signal from U3 (pin 14) is supplied to the pin 11 of U1 and sent to the telephone
line.
9. Pulse dialing
In case that the phone is in pulse dialing mode, it is possible to use pulse dial.
The pulse signal is made by switching Q3 (switching TR) on and off by
PULSE_CON(CPU pin 30).