Multi-Tech Systems MT5600SMI-L34, MT5600SMI-XL34, MT5600SMI-P92, MT5600SMI-PL92 Rxd, 3V DC Power

			Chapter 2 – Mechanical Specifications
Pin	Signal	I/O	Description
#	Name	Type
31	DTRIND		DTR LED. Output from 74AC05 with 1500 Ohms pull-up.
32	TXIND		TX LED. Output from 74AC05 with 1500 Ohms pull-up.
33	–RTS	I	Request to Send. RTS signal is used for hardware flow control.
34	–RXD	O	Received Data. Used to send data received from the telephone line and also
			modem responses to the DTE. Modem response take priority over incoming
			data. When no data is transmitted, the signal is held in mark condition.
35	–TXD	I	Transmit Data. The DTE uses this line to send data to the modem for
			transmission over the telephone line or to transmit commands to the modem.
			The DTE should hold this circuit in the mark state when no data is being
			transmitted or during intervals between characters.
36	–RI	O	Ring Indicate. –RI output ON (low) indicates the presence of an ON segment
			of a ring signal on the telephone line.
			The modem will not go off-hook when –RI is active; the modem waits for –RI
			to go inactive before going off-hook.
37	–DSR	O	Data Set Ready. –DSR indicates modem status to the DTE. –DSR OFF
			(high) indicates that the DTE is to disregard all signals appearing on the
			interchange circuits except Ring Indicator (–RI). It reflects the status of the
			local data set, and does not indicate an actual link with any remote data
			equipment.
38	–CTS	O	Clear To Send. –CTS is controlled by the modem to indicate whether or not
			the modem is ready to transmit data. –CTS ON, indicates to the DTE that
			signals presented on TXD will be transmitted to the telephone line. –CTS OFF
			indicates to the DTE that it should not transfer data across the interface on
			TXD.
39	–DCD	O	Data Carrier Detect. –DCD output is ON (low) when a carrier is detected on
			the telephone line or OFF (high) when carrier is not detected.
40	–DTR	I	Data Terminal Ready (Active Low). The –DTR input is turned ON (low) by
			the DTE when the DTE is ready to transmit or receive data. –DTR ON
			prepares the modem to be connected to the telephone line, and, once
			connected, maintains the connection. –DTR OFF places the modem in the
			disconnect state.
41	DGND		Ground.
61	VCC		3.3V DC Power.
63	AGND		Analog Ground. Analog ground is tied common with DGND on the
			SocketModem. To minimize potential ground noise issues, connect audio
			circuit return to AGND.
64	SPKR		Speaker Output. SPKR is a single ended-output. SPKR is tied directly to the
			CODEC. One side of a differential AC output coupled through a 6.8K ohm
			resistor and capacitor.
			The call progress speaker interface signal is:
			￿ Digital speaker output (DSPKOUT); output
			DSPKOUT is a square wave output in data mode used for call progress or
			carrier monitoring. This output can be optionally connected to a low-cost on-
			board speaker, e.g., a sounducer, or to an analog speaker circuit.

Multi-Tech Systems, Inc. SocketModem MT5600SMI Developer’s Guide 10