Problems

1. Referring to the circuit of Fig. 22, calculate the magnitudes and indicate the directions of the current flowing in each part of the circuit with the keys at each station in the positions shown. Determine whether each relay armature, with the magnetic polarities indicated, will rest on the marking (m) or the spacing (s) contacts.

Figure 22. Simplified differential duplex system showing typical resistance values. (Adapted from Reference 14.)

2. Repeat Problem 1 for each of the four possible positions of the sending and receiving keys, drawing the equivalent circuits and indicating the magnitudes and directions of the currents on these circuits, and also showing the resulting relay positions.