# TTY-related issues

The following table lists the problems that are associated with making or receiving TTY calls using Avaya one-X Agent.

Problem description | Recommended action
--- | ---
Whenever a caller with hearing disabilities places a call to an outside number using the TTY option: TTY returns with the error message while making conference: `Operation Failed Create Conference Failed.` | This problem occurs when an agent tries to conference a call while on a TTY call. Avaya one-X Agent does not support conferencing on a TTY call.
If an agent loses the first character in a call from a caller during a TTY call, TTY will not work. | Verify one or all of the following: Agent has the latest firmware on Media Gateway (G430 or G450) and or circuit packs (TN2602). TTY requires firmware version 30.13.2 or higher for G430 or G450 gateways and firmware version 55 or higher for TN2602 and circuit packs. Your organization is using Communication Manager 5.2.1 or later, as TTY will not work on Communication Manager 5.x and has higher rates of character loss on older releases.
If agents enter a numeric characters when a TTY call is on hold, the system displays wrong characters at the called-party's TTY device. TTY stops working if Multiple Level Precedence and Preemption (MLPP) is set. | Verify one or all of the following: Ensure that MLPP is disabled. The option is available on the `system-parameters customer-options` settings on page 5 of Communication Manager user interface. Ensure that you are using Communication Manager 5.2.1 SP2 or later.

Parent topic: Troubleshooting overview
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