metallic-circuit

_ Fig. 278 shows how the same cord circuit and the same arrangement of line equipment may be used for connecting a grounded line to a metallic-circuit line.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910

The left-hand conductor of the metallic-circuit line will be connected to ground because it will be continued through the sleeve strand of the cord circuit to the sleeve contact of the calling plug and thence to the sleeve contact of the jack of the grounded line, which sleeve contact is shown to be grounded.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910

A better way of connecting a metallic-circuit line to a grounded line is by the use of a special cord circuit involving a repeating coil, such a connection being shown in Fig. 279.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910

The talking circuit between the two connected lines in this case may be traced as follows: From the subscriber's station at the left through the right-hand limb of the metallic-circuit line, through the tip contact and tip conductor of the cord circuit, to the single limb of the grounded-circuit line, thence to the sub-station of that line and through the talking apparatus there to ground.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910

The two inner springs form the terminals for the two limbs of the metallic-circuit line, while the two outside springs are terminals for the continuation of the line leading to the switchboard.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910

Thus, when the cord circuit of a metallic-circuit switchboard is used to connect two grounded circuits together, the tip strand of the cord is the connecting link between the two conductors, while the sleeve strand of the cord merely serves to ground one side of the clearing-out drop and one side each of the operator's telephone set and the ringing generator when their respective keys are operated.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910

The reason for this is that while many grounded circuits are still in use, there are very few places where there are not some metallic-circuit lines, and while the grounded-circuit switchboard will not serve for metallic-circuit lines, the metallic-circuit switchboard will serve equally well for either metallic-circuit or grounded lines, and will interconnect them with equal facility.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910

When grounded circuits were the rule rather than the exception, many of the switchboards were particularly adapted for their use and could not be used with metallic-circuit lines.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910

The return path from the right-hand station is by way of ground to the ground connection at the central office, thence to the sleeve contact of the grounded line jack, through the sleeve conductor of the cord circuit, to the sleeve contact of the metallic-circuit line jack, and thence by the left-hand limb of the metallic-circuit line to the subscriber's station.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910

_ In Fig. 276 a common magneto cord circuit is shown connecting two metallic-circuit lines; in Fig. 277 the same cord circuit is shown connecting two grounded lines.

Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. George Patterson 1910