Without knowing which system you are referring to, it's hard to say. If it is an sts or xts you would need to program button 01 on the slt ext as a pool or line key. Then you would enable button 01 for offhook button preference. Both are done in flash 51 page b. Don't forget to make sure your lines are assigned to the pool group and that unused lines should be in a group other than 01. Use 00.

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