| Switchboard BD-71/72 | |||
| my personal BD-72 | Wiring diagrams | TM11-330 excerpts | Hacked BD-71 |
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 BD-71 / BD-72 Wiring Diagram |
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| Switchboard BD-71/72 are 6 line and 12 line minimal modernizations of the WWI EE-2 switchboard. BD-71/72's offered improvements such as an operators set made from EE-8 components. A buzzer was substituted for the normal ringer. Fixtures to hold batteries for the buzzer, lights to see the drops and for the operator's microphone were also included. A thumb screw terminal block for easy line installation was added in the rear of the unit. This terminal block also included arc/spark gap surge protection. This removed the need for the fuses found on WWI EE-2 switchboard/drop/line units. The void left by the fuses was used for 3 position switches to connect to the operators set and ring generator. Information from http://www.royalsignals.org.uk Document # 670 (EE-2, The Monochord Switchboard, USSC Electrical Eng. Pamphlet No 2, 30/6/1918) 
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