Dennis,
Sorry for the late reply...I was occupied in another discussion, but I'm free of that now.
I'm writing a detailed description of the Marconi apparatus, but it won't be published until 2004. I don't want to give too much away before then, especially since my analysis of the wreck footage is still ongoing. The Antique Wireless Association, though, published a condensed version of my draft for their members a couple of months ago, so I'll quote from that:
<font color="#000066">Accumulators – A battery of 8 chloride accumulators stored direct current from the ship’s mains for use by the wireless set in the event of a shipboard electrical casualty. During normal operation, the accumulators were charged by the ship’s dynamos and required little attention. Upon loss of power from the ship’s mains, the operator could discharge the accumulators through a 10” induction coil by using the Emergency Key. Eight accumulators were provided in order to provide the necessary E.M.F. to work the emergency spark coil. The cells in each battery were arranged in series, with positive connected to negative, leaving a positive terminal at one end and a negative at the other. Cells were deep enough to allow the lead plates to be covered with dilute sulphuric acid at all ordinary angles of heel. The movement of the ship actually helped the accumulators keep the electrolyte at a uniform specific gravity, as it kept the acid from settling in layers of varying densities. The acid would boil toward the ends of charging, but spraying was prevented by covers. The operator had to ensure that no naked-flame lights were used near the cells when the accumulators were fully charged, because the amount of hydrogen released during the process could be ignited by contact with a light source. The operator monitored the voltmeter mounted on the Charging Switchboard during operation of the emergency set to guard against the occurrence of sulphating in the accumulator cells, a condition where the lead plates were coated with a white insulating skin of sulphate of lead which rendered the plates electrolytically inert and gave the cell a high resistance and low capacity. Normal (non-emergency) discharging of the cells had to be terminated when a reading of 14.5-15 volts was indicated; otherwise, permanent sulphating of the cells would occur.
Charging Switchboard (Fig. 29) – The switchboard used for the emergency set was a Marine Type Switchboard, No. 1. The operator could control the discharging and charging of the accumulators through use of multi-point switches on the switchboard. The position of the double pole three-way switch connected the ship's dynamos to the accumulators and determined the direction of the charging current through the battery. Two 50 c.p. carbon filament lamps provided a visual indication that the proper connection had been made for charging the batteries. The position of the D.P. switch that provided proper charging would cause the lamps to glow least brightly. The single pole three-way switch was used to connect the induction coil into the circuit. A 15-ampí¨re fuse inserted between the coil and accumulator terminals along the bottom of the switchboard protected the coil when working off the accumulators; the two connected to the fuse terminals protected the coil from the main charging and working circuits. Because the accumulators were not used in normal operation, a series of twelve 4-ohm charging resistance coils were inserted into the charging circuit to slow the charging rate. The filament lamps were wired in series with the charging circuit and allowed a charging current of 4-ampí¨res to pass. Since the charging rate of the battery was nominally 12-ampí¨res, long charges were required to fully refresh a depleted battery. When the battery of accumulators was fully charged and charging current still passing, the operator would read approximately 20.8-volts on the supplied voltmeter. At that point, gas would be freely bubbling from both positive and negative plates. With the charging current removed, the reading fell to around 17-volts, or 2.1-volts per cell. Because permanent sulphating would occur when the voltage in any individual cell in the battery fell below 1.85, the operator took care not to allow the total voltage as shown on the voltmeter to fall below 14.5-15-volts, which equated to 1.17 specific gravity of the acid.
I'll have more detail in my final work. In addition, you'll be able to see the battery boxes in the re-creation of the Silent Room in the "Ghosts of the Abyss" companion book coming out in March.
As far as duplicate components were concerned: Titanic carried two receivers. The Magnetic Detector/Multiple Tuner was the receiver most used as it was simple and "sailor-proof." A Marconi Fleming-valve receiver sat next to the Multiple Tuner and could be switched into the circuit via a two-way switch. The valve receiver needed a 4-volt source to power the valves' filaments, so 2 battery boxes and a charging switchboard were supplied in the Marconi Room (also visible in the Marconi Room re-creation in the "Ghosts" book). The valve receiver was actually a better receiver than the "Maggie"/tuner combination, but took more skill to operate. Both would eventually be replaced by crystal sets.
As far as transmitters are concerned, a spark could be generated using both windings of the transformer, one winding of the transformer (reduced output), or via the induction coil of the Emergency Set. There were two spark gaps...the disc discharger at the aft end of the motor-generator set in the Silent Room and on the induction coil in the Marconi Room. A buzzer was supplied that was used for extremely close-range communication and circuit testing, but the noise it created wouldn't carry very far.
There were two switches to cut ship's power from the set, 4 condensers, two windings in the transformer, 8 accumulators for the Emergency Set...all these were needed for normal operation, but they could be reconfigured in the event of a casualty.
Parks
