The MC3453 and MC3553 feature four line drivers with a common-enable input. When the ENABLE input is high, a constant output current is switched between each pair of output terminals in response to the logic level at that channel input. When the ENABLE is low, all channel outputs are nonconductive (transistors biased to cutoff). This minimizes loading in party-line systems where a large number of drivers share the same line. The driver outputs have a common-mode voltage range of 3 V to 10 V, allowing common-mode voltages on the line without affecting driver performance.