circuits from the source of power using knobs with built-in automatic shielding devices; 3) the use of three-position switches with manual control, which excludes short circuiting in switching circuits. Special measures, as noted above, were taken in the control of the lock drive of the docking frame and in the construction of elements of the circuit; for example, a three-position switch was used to control the drive, and this switch was covered to prevent accidental switching and consciously making the control procedure more complicated. Tn individual cases on the Apollo the possibility was provided of switching on electromechanical devices including the docking device (drives and pyrotechnics) by direct application of power to the electrical connections, by-passing the commutating elements and the terminal switches. This was done with a cable connected manually by the astronauts. Tn the docking device of the Apollo and the APDA of this craft, the devices to release the latches used electromagnets with a rotor for rotary and forward displacement. Compared to the electrical engines the electromagnets had their own advantages and disadvantages. The schematic of electromagnet control is usually simpler (no terminal switches are required), however, the commutated current is relatively large . For comparison we note that the current in the drive to release the latches of the Soyuz APDA was significantly smaller (start-up current = 0.6 A, nominal current . The electromagnets are used in conjunction with lever mechanisms, whose size and mass are somewhat smaller than the mechanisms with the electrical drives. However, the lever mechanism is more sensitive to clearances and gaps in the parts, and the magnets usually have a limited course. The circuits for commutation of the electrical engines of the docking device drives with remote control are usually designed with a consideration of the following basic requirements: They should execute control commands, including brief (lasting several tenths of a second) “forward” and “backward” commands coming from the control panel, from the command radio line, and from automatic devices;
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