INSTRUMENT, EXTENSION, CB No. 20

The description includes Case for Extension Instrument, C.B. No. 20; fitted with Bell, Magneto, 1,000 ohms (unmounted); Coil, Retardation, Type 9A (80 + 80 ohms) ; Switch, 3-position, Drawing 926; 2 Condensers, metal-cased, 2uf; and Switch spring, 5-point.

Calls from P.O. Exchange are received on the Magneto Bell, and answered by turning the Switch to "Exchange" position and inserting peg in Switch spring. If an Extension is wanted, Peg should be withdrawn and inserted in Switch spring of Extension asked for on N.T. Company's Switch. The Extension should then be called as usual from N.T. Company's Telephone and after replying should be connected to the Switch spring on this instrument.

Clearing Signal from Extension is received on the Magneto Bell, and the clearing signal to the Exchange is sent by restoring the Switch to normal.

Calls from the Extension are received on N.T. Company's Indicator. The Extension is then pegged through to Switch spring on this instrument, and the Exchange is called by the action of turning Switch to "Exchange" position.  Clearing signal as before.  The movement of the 3-position Switch to the left should be blocked.


C.B. Diagram - No. 20.