a telephone using conventional telephone mechanical and electrical components mounted within a telephone housing , typically mounted on a wall , with the earpiece and mouthpiece mounted to be protected by the telephone housing . the housing has a front face surrounded by tapered edges , which provide angled transitions from the front face to the mounting surface . to operate , the user pushes an on / off switch and places an ear next to the fixed earpiece . the telephone is designed for use in prisons , so inmates within a prison cannot hang themselves with a handset cord or break a handset and handset cord off for use as a weapon . the tapered edges restrict access to the abrupt sides of the rigid housing , so the phone does not protrude as a blunt object from the wall . the telephone , which may include a payphone escrow system , is also suitable for use in any high crime or remote public areas to reduce the potential for vandalism . the telephone design reduces the cost of maintenance by eliminating the need to fix and replace a telephone handset , or damaged housings .