An endless tape provides 30 min recording time for audio signals input on four separate channels. The channel inputs are captain's, first officer's and flight engineer's transmitted and received audio and cockpit area conversation. Passenger address audio may be substituted for the flight engineer's audio in an aircraft certified to fly with two crew members.
The microphone inputs should be from so-called 'hot mics', i.e. microphones which are permanently live regardles of the setting of ASP or control column switches. The area microphone (which maybe separate from the control panel) is strategically situated so that it can pick up night crew speech and general cockpit sounds.
While the control panel is situated in the cockpit, the recorder unit (CVR) is located at the other end of the aircraft where it is leastlikely to suffer damage in the event of an accident. The CVR is constructed so as to withstand shock and fire damage, and additionally is painted in a fire-resistant orange paint to assist in recovery from a wreck.
The recorded audio may be erased providing the landing gear and parking brake interlock relay contacts are closed. As a further safeguard against accidental erasure a delay is incorporited in the bulk erase circuit which requires the operator to depress the 'erase' switch for two seconds before erasure commences.
The recorded audio may be erased providing the landing gear and parking brake interlock relay contacts are closed. As a further safeguard against accidental erasure a delay is incorporited in the bulk erase circuit which requires the operator to depress the 'erase' switch for two seconds before erasure commences.
Test facilities are provided for all four channels, separately or all together. A playback head and monitor amplifier allows a satisfactory test to be observed on meters or heard over a headset via jack plug sockets. Pressing the test button on the control panel or the all-test button on the CVR causes the channels to be monitored sequentially.
The power supply for the system should be from a source which provide maximum reliabilitv. Since the tape is subject to wear and thus has a limiied life, the CVR should be switched off when nqt in use. A suitable method would be to remove power to the CVR whenever external ground power is connected.
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