Allied Telesis AT-x510-28GTX Installation Manual page 53

Here are the transceiver guidelines:
The stacking transceivers may only be used in the stacking slots

and only with the VCStack feature. You may not use the
transceivers as regular networking ports.
The AT-StackOP/0.3 and AT-StackOP/9.0 transceivers must be

connected to other AT-StackOP/0.3 and AT-StackOP/9.0
transceivers. The transceivers do not work with other types of
network devices.
You may use different types of transceivers to connect the

switches of a stack and so build stacks of switches that are at
various distances from each other.
x510 Series Installation Guide for Virtual Chassis Stacks
53