Battery Connection Points
The labels indicate connections between the switchboard and batteries which power several of its components: O.P. Battery is a misnomer; it stands for "Operator Battery," which powers the operator's voice circuits.
N.A. Batt is where the power hooks up for the Night Alarm system, which rings a bell whenever a customer has requested service.
P. Gen is for an external "power generator" which provides ringing power, saving the operator the need to signal subscriber lines with the on-board magneto. Note the larger diameter wires for the power generator, which is AC instead of DC, and requires enough current to ring remote subscriber station ringer bells.
Also note that someone had jumpered together all three sets of connections. This is incorrect, in that two of them require DC and the third one (power generation) AC power. In the old days, before the electrical grid was established, such power was supplied by DC-powered devices known as pole changers.
Battery Connection Points
The labels indicate connections between the switchboard and batteries which power several of its components: O.P. Battery is a misnomer; it stands for "Operator Battery," which powers the operator's voice circuits.
N.A. Batt is where the power hooks up for the Night Alarm system, which rings a bell whenever a customer has requested service.
P. Gen is for an external "power generator" which provides ringing power, saving the operator the need to signal subscriber lines with the on-board magneto. Note the larger diameter wires for the power generator, which is AC instead of DC, and requires enough current to ring remote subscriber station ringer bells.
Also note that someone had jumpered together all three sets of connections. This is incorrect, in that two of them require DC and the third one (power generation) AC power. In the old days, before the electrical grid was established, such power was supplied by DC-powered devices known as pole changers.