Digital-Stopclock-with-External-Trigger-Rapid-TM-20A-p-The-TM-20A-is-a-high-accuracy-easy-to-use-unit-that-can-be-used-either-as-a-standard-timer-or-may-be-automatically-started-&-stopped-by-an-externally-connected-device-p-Rapid-TM-20A-Digital-Stopclock