Owner`s manual

PN 88300150
4/3/01 95
FUNCTIONAL DESCRIPTION OF MT2834MR RS232C SIGNALS:
Transmitted Data - Pin 2, SD (BA)
Direction: to modem
Signals on this circuit are generated by the customer’s terminal and transferred to the transmitter of the
MT2834MR. A positive signal is a space (binary 0) and a negative signal is a mark (binary 0). The
transmitting terminal should hold this line in the marking state when no data is being transmitted,
including intervals between characters or words. The TRANSMIT (SD) LED indicates the status of this
circuit.
Received Data - Pin 3, RD (BB)
Direction: from modem
The lead is the data output of the modem. Data signals received from the remote modem are presented
on this line. When no carrier signal is received (pin 8 negative), this line is forced into a marking
condition. The RECEIVE (RD) LED indicates the status of this signal.
Request To Send - Pin 4, RTS (CA)
Direction: to modem
The RTS signal indicates to the modem that the computer or terminal has data to transmit.
Clear To Send - Pin 5, CTS (CB)
Direction: from modem
The CTS line indicates to the terminal that the MT2834MR will transmit any data present on the Transmit
Data line (pin 2).
Data Set Ready - Pin 6, DSR (CC)
Direction: from modem
DSR ON, indicates that the MT2834MR is in the data mode and is connected to the communications
channel. This signal is on during analog-loop-test mode.
Signal Ground - Pin 7, SG (AB)
The SG lead is connected to signal ground of the modem. It establishes the common ground reference
for all other interface signals.
Data Carrier Detect - Pin 8, CD (CF)
Direction: from modem
DCD On (positive voltage) indicates that data carrier has been received from the other modem. This
circuit does not typically turn on in the presence of message circuit noise or out-of-band signals. There is
a one second delay between when the carrier tone is detected and when the CD circuit is turned on.
This signal goes off if received data carrier falls below the receiver threshold for more than 37 mSec.
When CD is off, the Received Data circuit (pin 3) is held to the marking state.
Test Voltage - Pin 9, XV
Direction: from modem
The XV lead has 330 ohms of resistance to +12 volts DC. This lead may be used to strap other signals
high. For example, if the terminal does not supply a DTR (Data Terminal Ready) signal, Pin 9 may be
jumpered to Pin 20 (DTR) on the RS232 connector or in the cable to force DTR on.
High Speed - Pin 12, HS
The On condition of this circuit indicates that the modem is in the high speed (1200 bps) mode. This
circuit is commonly used to signal the computer or terminal to which the modem is connected to switch to
its 1200 bps setting.