Allied Telesis AT-S39 - Manual (Page 109)

Section II: Local and Telnet Management
109
4 - Edge Port
This parameter defines whether the port is functioning as an edge
port. For an explanation of this parameter, refer to Point-to-Point
Ports and Edge Ports on page 97.
M - MCHECK
This option instructs the bridge to send out RSTP BPDU packets
for several seconds from the selected port. The purpose is to
determine if there are any RSTP or STP bridges connected to the
port. If the port receives STP BPDU packets in response, the port
changes to STP compatible mode. If the port receives RSTP BPDU
packets, it operates in RSTP.
7. After making your changes, type S to select Save Configuration
Changes.