User's Manual

This is the positive power supply input for the modem.
Pin 7 Receiver Alginment
This pin is the output pin of the modem IC’s input operational amplifier. It is used during alignment to set
the receiver gain and DC offset for proper modem IC receiver decoding. This pin must be left
unconnected by the user!
Pin 8 RD (Receive Data)
RS-232 data to be received from the modem is available at this pin. The data are at normal RS-232 levels
and are transmitted from the modem to be received by the host computer or other device connected to
the modem.
Pin 9 TD (Transmit Data)
RS-232 data to be transmitted to the modem should be presented to this pin. The data should be at normal
RS-232 levels and are transmitted from the host computer or other device to the modem.
Pin 10 CTS (Clear to Send)
This RS-232 output pin is asserted by the modem as a response to an assertion of the RTS pin when it is
ready and able to receive data from the host computer or device.
Pin 11 DSR (Data Set Ready)
This RS-232 output pin is asserted by the modem when it is powered-up. It indicates that the modem is
actually connected, although not necessarily ready to receive data. The polarity (active low/active high) is
programmable via the programmer.
Pin 12 TEST (Voice mode PTT)
This pin in used to key the transmitter. When asserted (taken low), this pin activates the voice/analog
transmit audio path and keys the transmitter, or transmits data test patterns.
Pin 13 CD (Carrier Detect)
This pin is asserted by the modem when the receiver has detected a carrier. The RF level for CD assertion
is set via the programmer. Note that the modem demodulation circuitry does not actually use this signal to
determine that a valid data packet has been received. The polarity (active low/active high) is
programmable via the programmer
Pin 14 RTS (Request to Send)
This RS-232 input pin is asserted by the host computer or device to indicate that it has data to be
transmitted by the modem. If the modem is able to accept the data, the CTS pin will be asserted in
response.
Pin 15 GND (Ground)
The system ground common point and negative connection for the power supply input.