A transistorized refraction seismograph has been developed based on pulse systems techniques. This results in direct visual time indications, major reductions in operating complexity, size, and weight, and the elimination of the necessity for photographic processing and the use of explosives. A 4‐kc crystal oscillator serves as the time base. The signal passes through a gate circuit to an electronic counter; the gate is opened at the time a sound wave enters the earth and is closed at the time the sound reaches a detector on the surface. The time‐distance data can be interpreted in terms of depths to subsurface layers and the nature of subsurface materials.