Communications System

TM 5-4220-226-14&P 1-14. Life Support System - continued. d. When the steady flow system is on, air that is not being inhaled by the diver flows through the main exhaust system and out into the water. The main exhaust valve is located at the lowest point in the helmet (when in a normal working or swimming position) so the slight overpressure created by the incoming steady flow air automatically ejects any water that may be present in the helmet. WARNING If emergency air supply valve is inadvertently opened before or during a normal dive, it can deplete the entire emergency air supply. e. Another inlet to the side block assembly is fined with an emergency valve. It is strongly recommended that the working diver carry an independent supply of air which is fitted with an air reduction valve and hose to the inlet of the emergency air valve. A high quality, high flow SCUBA first stage regulator may be used for this purpose. Be sure it is fitted with a relief valve for overpressurization of the supply hose. Air flow from the emergency valve enters the side valve and follows the same route as the main supply. 1-15. Communications System. a. A pair of dynamic speakers for earphones and a matching rnicrophone are standard equipment in the helmet. Each unit is wired in parallel and connected to the communications whip at the two communications posts inside the helmet. The earphones differ from each other only in the length of the wires. b. The earphones and microphone must "breathe" or equalize as the internal pressure changes. Tiny tubes surround the wires of these units and allow slight amounts of air to flow through the tubes. 1-6