RJR is correct. A Power Programmer has nothing to do with a charging port in a tender. It is wired between a transformer and the track. It quickly selects RESET Positions.
QSIndustres introduced the first successful electronic E-unit around 1983. Sound systems followed. These units became more complex as QSI moved toward a Conventional version of Command control. RESET Positions set Engine ID, Train ID, chuff rates, volume, Whistle in Neutral, Passenger or Freight Station Announcements, and a host of others.
Before Command control, these features were accessed and programmed (Whistle ON or OFF in Neutral, for example) in RESET positions. When track voltage was turned on (10 volts or less), an engine powered up in RESET. The first was Position 1. Subsequent Positions were accessed by turning track voltage up to 16 or 20 volts, then down (but not OFF) to about 6 volts. A "clink" sounded for each Position. A "clank" sounded at Position 5 and another at Position 10 and so on. To set the Chuff Rate in Position 27, track voltage was turned up and down until an operator heard 5 "clanks" and 2 "clinks": (5 + 5 + 5 + 5 + 5 + 2). As Reset Positions increased, a Power Programmer was introduced to speed up the process. Power Programmers evolved into SideKicks I and II. They replaced up/down motions of a transformer handle with high and low voltage. They also sent strong postive DC (+) for whistles and horns and negative DC for bells (-).