Switchable phase lock loop for dual mode applications

A dual-mode wireless telephone which is capable of operating on two different bands of frequencies. The dual-mode telephone having a single phase lock loop combined with a single local oscillator that can select between two frequencies in two widely spread output frequency bands such as the bands in the GSM and DCS standards. A switch in the phase lock loop selectively swaps an UP signal and a DOWN signal to achieve either a high side lock or a low side lock. When the phase lock loop is high side locked, a target frequency in a higher band of output frequencies is generated. When the phase lock loop is low side locked, a target frequency in a lower band of output frequencies is generated.