CTI Products NCB/EM with External PSTN Modem - Manual (Page 55)

CTI Products, Inc. NCB-EM User Guide
Appendix G. Modem Notes 49
A PPENDIX G. M ODEM N OTES
Manual Dial-Up Mode (PSTN)
Manual dial-up mode requires command information be sent to the originating NCB unit to cause it to dial the
answering NCB unit. This command information is sent in the form of Network Variables bound to function
blocks (objects) of the control Neuron processor inside the NCB module. The detail of these function blocks
and network variables is provided in the S
ECTION 3, N ETWORK V ARIABLE C ONTROL
This command information can be sent by any LonTalk node connected to the “NETWORK” port of the NCB
unit to be dialed. Additionally, a DOS utility program called NCBCON.EXE, included with each NCB unit,
can be used to send this command from a simple menu. See Technical Note TN023 for more information on
this program.
After receipt of a dialing command, the originating NCB module will go offhook and perform the dialing
sequence. If a dial-tone is not detected within 4 seconds after going offhook, the NCB module will return
onhook and await a new dialing command. Once the dialing sequence is complete, it begins the training
sequence, waiting for an answer tone from the distant NCB module.
The NCB module configured in the Dial-Up ‘Auto Answer Enabled’ mode (the one being dialed) will detect the
incoming ring on the telephone “LINE” connection. At the end of the first ring, it will go offhook and respond
with an answer tone after a 2 second period of silence. The training sequence determines telephone circuit
characteristics, sets appropriate equalization parameters and other housekeeping items, and concludes with the
"CD" (carrier detect) LED illuminating. Within 2 seconds after this LED lights, data packets can flow across
the modem connection and the simultaneous voice/data facility is enabled on the “AUDIO” connector.
The elapsed time between training sequence start (the end of the dialing sequence at the originating NCB
module) and training sequence completion (carrier detected) is tracked by a timer inside each NCB unit. If the
time reaches 60 seconds and training has not concluded, the NCB units will go onhook. The originating NCB
module will await a new dialing command and the answering NCB module will wait for another ring. When
configured for manual dialing mode, no automatic redialing is performed. Once a connection is established
between the two NCB modems, any loss of carrier will be detected by both NCB modules and cause them to go
onhook and await new commands/rings. Data entering the NCB module from the “NETWORK” or control
Neuron processor ports while the modem is not in the connected state is not buffered.
Perpetual Dial-up Mode
The NCB module can be configured to provide a “perpetual” connection using the ‘dial-up’ mode of the
modem, with no runtime user or application intervention required to initiate or maintain a constant modem
connection. This closely approximates the operation of Leased-Line mode, but uses dial-up mode.
Operationally, the NCB unit used in Perpetual mode is configured with the telephone number of the remote
NCB unit. (The remote NCB’s modem must have Auto-Answer mode enabled.) When powered on, the unit in
Perpetual mode automatically dials the remote unit and the connection occurs without user or application
intervention. Should the link between the two modems not connect or be broken for any reason, the unit in
Perpetual mode will automatically redial the remote unit and re-establish the connection.
Note that NCB modules configured with the modem approved for use in the United Kingdom do not include
this perpetual dial-up feature.
The NCB/Plug plug-in can be used to configure the NCB for Perpetual Dial-Up Mode. (See section “4.
NCB/P LUG
”.)