Data Comm for Business, Inc.

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Product Application Note

SPL Multiplexers, ISDN and One Touch Dial

By: Russ Straayer, Data Comm for Business, Inc.

SPL One Touch Dial is a feature that will automatically cause the link to be dialed and connected when there is terminal traffic, and disconnect when there is no terminal traffic. The disconnect timer can be set for a value of 1 to 99 minutes. A user at any terminal on any port of the remote SPL can cause the connection to take place by entering the space bar character or pressing the enter key (carriage return).

One Touch Dial is a high performance, low cost way to use ISDN dial up for users with low traffic volume from a remote office to the host computer. With One Touch Dial, charges accrue only when someone is using the link, not all day long. And, ISDN connects and disconnects almost instantly. Connection takes less than half a second, disconnection takes just a few milliseconds.

How to set up One Touch Dial

Host End ISDN TA and SPL:

1. Set the ISDN TA to synchronous, auto answer.

2. Set the SPL to synchronous leased line operation. Switch position 2 of the 6 position DIP switch must be up, the other 5 positions down.

Remote End ISDN TA:

1. Configure for persistent DTR (not ignore DTR).

2. Configure Carrier Detect as normal (not forced on).

3. Configure register S0 with the phone number that is to be dialed.

4. Configure for synchronous operation.

Remote End SPL:

1. 6 Position DIP switch - set all 6 positions down for dial up, synchronous operation.

2. Using the SPL NMP port or port 1 set up, set the Disconnect Timer options as follow:

Lan Diagram one

3. The +12/-12 jumper must be moved to the right position to enable DTR controlled disconnect. The location of the jumper is shown below:

Lan Diagram one


Lan Diagram one

Russ Straayer is president of Data Comm for Business, Inc. He is a graduate of the University of Illinois with more than 20 years of experience in voice and data networking. He has been an instructor in data and telecommunications, and has consulted for a number of fortune 500 companies. His Email address is

Data Comm for Business, Inc. is a manufacturer and distributor of a diverse line of data communications and networking products. Their experts can help you connect remote sites with phone (1-800-4-dcbnet), email (, or personal (807 Pioneer, Champaign, Il. 61820) assistance. Check out their Web page at .