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Home Telephone Toll Service and Systems The 22-Type Repeater | |||
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The 22-Type RepeaterThese limitations are largely overcome in the 22-type repeater12,15 shown in Fig, 8. Two amplifying elements are used, and each line is balanced by a network. Thus, lines of different characteristics may be connected to the repeater without causing singing. Assume that a voice-frequency signal comes in over line west. The energy will divide at the bridge transformer, one half being dissipated in the output circuit of element 2 and the other half entering the input circuit of element 1. This energy is then amplified and introduced into line east, where it divides, one half being lost in the balancing network and the other half flowing over the line to the distant listener. Thus, in order for a 22-type repeater to sing, an unbalance must exist between each line and its balancing network; that is, the west bridge transformer must be unbalanced to introduce energy into the input of element 1, and the east transformer must be unbalanced to permit energy flow into the input of element 2 and again couple with the west transformer. The purpose of the low-pass filter shown in Fig. 8 is to eliminate currents above the voice-frequency range, thus making it unnecessary for the balance between the line and the network to hold accurately at high frequencies. This amplifier has been widely used in telephone systems.
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Home Telephone Toll Service and Systems The 22-Type Repeater |