sipates (as heat) in the impedance of the four-wire side receive path and the other half goes to the four-wire side transmit path, as illustrated in Figure 4.15. Here the ideal situation is that no energy is to be dissipated by the balancing network (i.e., there is Four-wire transmit Balancing network (N) Two-wire connection (L) Four-wire receive Figure 4.15 Operation of a hybrid transformer. 4.4 ESSENTIAL CONCEPTS IN TRANSMISSION a perfect balance or impedance match). The balancing network is supposed to display the characteristic impedance of the two-wire line (subscriber connection) to the hybrid.¹4 Signal energy entering from the four-wire side receive path is also split in half in the ideal situation where there is a perfect balance (i.e., a perfect match). Half of the energy is dis- sipated by the balancing network (N) and half at the two-wire port (L) (see Figure 4.15.) The reader should note that in the description of a hybrid, in every case, ideally half of the signal energy entering the hybrid is used to advantage and half is dissipated or wasted. Also keep in mind that any passive device inserted in a circuit, such as a hybrid, has an insertion loss. As a rule of thumb, we say that the insertion loss of a hybrid is 0.5 dB. Thus there are two losses here that the reader must not lose sight of: Hybrid insertion loss 0.5 dB Hybrid dissipation loss 3.0 dB (half of the power) 3.5 dB (total) As far as this section is concerned, any signal passing through a hybrid suffers a 3.5-dB loss. This is a good design number for gross engineering practice. However, some hybrids used on short subscriber connections purposely have higher losses, as do special resistance-type hybrids. In Figure 4.15, consider the balancing network (N) and the two-wire side of the hybrid (L). In all probability (L), the two-wire side will connect to a subscriber through at least one switch. Thus the two-wire port on the hybrid could look into at least 10,000 possible subscriber connections: some short loops, some long loops, and some loops