Toshiba GD-1270, GD-1260, GD-1250 Monitoring signal, Line Monitor, LOW High, Ringer/Alarm, Low

EU/AU/AS/C models

NCU board (Line1)

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
						IC6
		+12V			AG		R11 1
			1	12	5	7		1	15		6
							2	0
											3
							13	1	14
								0
								11	10
					Q4
					AG
									NCU board (Line2)

Speaker

SP+

SP-

FAX board

	1	TXOUT1
CN501	2	RXIN1			2
					1
	6
	3
				13	14
					R273
				14
					R272
				15
					R271
CN502	2	RXIN2		12
					R270
			IC9	1
			[IC2]
			Analog		R268
				5
			switch
					R267
				2
		IC10[IC1]			R266
CN503	1	5	3	4
	2
		SG		11 AG
				10
				9

IC3

Analog

switch

28,29[25,26]	IC12
	[IC9]
32[9]	MODEM

			IC45
12	RING	43	[IC12]
			CPU
9	MF-SEL	6
10	SP-SEL	15
11	MON	26
	ATT3DB1	22	IC29
			[IC26]
	CML1	21
			ASIC
	VOLSEL0	16
	VOLSEL1	17
	VOLSEL2	18

Fig. 4-14

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), the ASIC (IC29 [IC26]) and analog switches (IC3, IC9 [IC3, IC2]) on the FAX 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 (IC3) according to SP-SEL signal and MON 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. 4-5 "4.2.2 Line path switching control circuit".

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

	Monitoring signal		SP-SEL	MON
LINE Monitor		Line 1	LOW	HIGH
		Line 2	HIGH	HIGH
Ringer/Alarm			-	LOW

The monitoring signal selected by IC3 is input to the analog switch (IC9 [IC2]) to select the output sound volume. The sound volume is selected by switching IC8 according to the VOLSEL0-2 signals output from the ASIC and selecting an input resistance for the monitoring signal.

GD-1210/1250/1270/1160/1260	© 2006 - 2011 TOSHIBA TEC CORPORATION All rights reserved
ELECTRICAL CIRCUITS

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08/04