For many years, the DT 109 has been the standard headphone /microphone combination for live, remote broadcasting, studio, film, TV and language laboratory application. Rugged, field-servicable construction. The headphone transducers feature extended frequency response. Adjustable, noise-cancelling microphone provides clear, audible speech transmission. Impedance 400 ohms as standard, other impedances to special order. Microphone 200 ohms as standard. Supplied as standard with straight cable which is terminated with female 4-pin XLR for Clearcom, ASL & Tecpro beltpack use.