With functions for calling, speech, door release, light, and storey call. Hearing protection and privacy function are integrated. Call silencing features a status display. It allows for a parallel connection of up to 4 bus telephones as standard (from the 3rd device, the PRI 602-... USB and ZBVG 650-... are required for programming). There is call differentiation for storey call, 2 door calls, and internal call. A door release button is included, and the light and call silencing button are freely configurable and double assignable. The call generator offers 11 call tone sequences, including a gong. Call volume is adjustable in 5 steps, up to a maximum of 83 dB(A). The door release and light function can be activated at any time via bus wires, and door release is possible at any time. An accessory connection relay ZAR 850-... can be retrofitted for the connection of an additional signal device. The base plate with connection terminals can be pre-installed. It can also be used as a table-top unit with the ZTS 800-... table-top accessory.