Avaya Definity TN768 Tone Clock (Refurbished)Key Features: Supplies timing, including Stratum 4 timing to the Port Network (PN) Produces the following tones: call progress, touch tones, answer back, and trunk transmission test Equipped with 2 MHZ, 16 kHz, and 8 kHz clocks Can transmit the system clock and tones on either Time Division Multiplexing (TDM) bus A, TDM bus B, or both Replaced by TN2182B Tone Clock Not necessary to replace TN768 with TN2182B in an upgrade TN768 is an acceptable tone