The M&S MC3 chime module has been discontinued. The M&S MC8 8-note chime module is the appropriate substitute.
The M&S MC3 3-note Chime Module is compatible with the DMC1 and DMC3-4 intercom master stations. When the bell button is pressed on a door station connected to the intercom the doorbell chimes. The 3 different chime options can be different for each door.