Techniques are disclosed for obtaining and maintaining synchronization of the TTR clock during a Channel Discovery Phase of DSL transceiver initialization for a DSL service operating in a TCM-ISDN crosstalk environment. The laser diode module includes a metal substrate mounting a laser diode chip and an optical component, and a peltier device thermally connected with the metal substrate. A projection of each reflecting sheet covers one LED element. The chamber has an inlet in flow communication with the channel and an outlet in flow communication with the plurality of fluid flow paths of the heat exchange tubes. An outer shell of the igniter is formed of the resin insulating material.