A call center handles TTY calls for the hearing and speech impaired. The mask includes a protrusion section that protrudes from a handling section of the mask. After drilling, the extension or another tool is used to remove the tips from the plate. The first and second contact layers are electrically connected to the first and second electrodes. Compound A2 and Compound A3, bicyclic carbohydrates with halogen containing aryl groups, possessed significant activity against Leishmania donovani, a parasite that causes leishmaniasis. The invention also relates to a filtering method of a corresponding kind.