Altec gsm socket al7024s Manuale Utente

AL7020S, AL7024S Designer’s Guide 

 

Doc. No. DG_7024E 

Altec Electronic AG  

Seite 11 / 32 

 
 
 

 
 

 
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The Serial interface signals are TTL-level signals. 

~RTSTTL IB 

Request To Send (TTL Active Low).  ~RTS is used to condition the local 
modem for data transmission and, during half-duplex operation, to control 
the direction of data transmission. 
On a full-duplex channel, RTS OFF maintains the modem in a non-transmit 
mode. A non-transmit mode does not imply that all GSM signals have been 
removed from the link. RTS OFF may be ignored if the modem is optioned to 
strap ~CTS ON; this allows the modem to receive from the DTE even though 
RTS is OFF. 
RTS input ON causes the modem to transmit data on TXD when ~CTS 
becomes active. 

~RXDTTL OB 

Received Data (TTL Active Low). The modem uses the ~RXD line to send 
data received from the telephone line to the DTE and to send modem 
responses to the DTE. Modem responses take priority over incoming data 
when the two signals are in competition for ~RXD. 

~TXDTTL IA 

Transmitted Data (TTL Active Low). The DTE uses the ~TXD 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. 

~CTSTTL OB 

Clear To Send (TTL Active Low). ~CTS is controlled by the modem to 
indicate whether or not the modem is ready to transmit data. ~CTS ON, 
together with the ~RTS ON, ~DSR ON, and ~DTR ON (where implemented), 
indicates to the DTE that signals presented on TXD will be transmitted. 
~CTS OFF indicates to the DTE that it should not transfer data across the 
interface on TXD. ~CTS ON is a response to ~DTR ON and ~RTS, delayed 
as may be appropriate for the modem to establish a connection.  

~RITTL OB 

Ring Indicate (TTL Active Low). ~RI output ON (low) indicates the 
presence of an incoming call.  

~DSRTTL OB 

Data Set Ready (TTL Active Low). ~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).  

~DCDTTL OB 

Data Carrier Detect (TTL Active Low). When AT&C0 command is not in 
effect, ~DCD output is ON when a link is established or OFF when no link is 
established.  

~DTRTTL IA 

Data Terminal Ready (TTL 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 and maintains the connection 
established by the DTE (manual answering) or internally (automatic 
answering). ~DTR OFF places the modem in the disconnect state under 
control of the &Dn command. The effect of ~DTR ON and ~DTR OFF 
depends on the &Dn command.