Toshiba GD-1220, GD-1221 Monitoring signal, Line Monitor, LOW High, Ringer/Alarm, Low

EU/AU/AS/C models

NCU board

RLY3

CML relay

							IC6
	4	Lb	1	5	T1	1	2				1
			4
			0
Line	CN3		1	8				IC3
										IC4
	3	La	9					Analog				CN4
			0						6	7	2
								switch
		+12V			AG	IC6	R11 1
			1	12	5	7		1	15		6
							2	0
											3
							13	1	14
								0
								11	10
					Q4
					AG

FAX board

	1	TXOUT1
CN252	2	RXIN1
	6
	3

28,29

[25,26]

IC2

32

[29] MODEM

3

IC9

Analog

switch

13

[4]15

R273

14[R31]

[2]

R272

15[R30]

[5]

R271

12[R29]

[1]

		R270
	1	[R32]
IC10	[12]

R268

Analog 5 [R35]

switch [15]

	R267
2	[R33]
[14]

12 RING 25

[2][SPKCLK]

9,10 TONESEL 59

11 RING/TONE 23

ATT3DB1 62

CML1 27

SPVOL0 58

SPVOL1 57

SPVOL2 24

CN5

MAIN board

	25	A5	IC53
			SoC
CN5	59	152
	23	153
	62	142	IC23
	27	144
	58	151	ASIC
	57	150
	24	149

Speaker

			IC10
SP+	CN264	1	5	3 3
SP-		2
			SG

R266

[R36]

[ 4 ] [R37] 13

11AG

Fig. 4-13

The line monitor circuit consists of the CML relay (NA/TW: RLY2, EU/AU/AS/C: RLY3), analog switch

(NA/TW: IC51, EU/AU/AS/C: IC3), analog switches (IC9, IC10) on the FAX board, ASIC (IC23) and SoC (IC53) on the MAIN board, and other peripheral devices. It switches the telephone line path using the analog switch and monitors the line status and ringer signal in the FAX transmission and reception using the speaker connected to CN503 on the FAX board. It also switches the analog switch to output a buzzer tone from the speaker.

The signal to be monitored is selected by switching the analog switch (IC9) according to TONESEL sig- nal and RING/TONE signal which are output from the ASIC.

To monitor the line during the transmission and reception, the ASIC makes the CML1 signal become HIGH to switch the analog switch and connect the line to the MODEM side.

For the line path switching control, refer to P. 4-4 "4.2.2 Line path switching control circuit".

The relation between the signal levels and monitoring signals is as follows.

Monitoring signal	TONESEL	RING/TONE
LINE Monitor	LOW	HIGH
Ringer/Alarm	-	LOW

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	ELECTRICAL CIRCUITS

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08/08