The transmitter is composed of both a PLL frequency synthesizer and a power amplifier. The synthesizer uses a voltage-controlled crystal oscillator, a dual-modulus prescaler, programmable frequency dividers, and a phase-detector. The power amplifier’s output power can be programmed to seven different levels. The MXR-505S has zero IF architecture which enables channel filtering with low-power, integrated low-pass filters. Each channel includes a pre-amplifier and a third order Sallen-Key RC low-pass filter that protects the switched-capacitor filter from strong adjacent channel signals. The main channel filter is a switched-capacitor implementation of a six-pole elliptic low pass filter. The cutoff frequency of the Sallen-Key RC filter can be programmed to four different frequencies: 100kHz, 150 kHz, 230 kHz, and 340 kHz. A receive signal strength indicator circuit indicates the received signal level. The MXR-505S is a well-designed transceiver suitable for a variety of RF applications, particularly voice applications and high volume OEM applications. The MXR-505S is for sale with and without an on-board microprocessor so that the user can manually address the module if that is required. Note: The MXR-505S is compatible with HHDS-ML-M but is NOT compatible with HHDS-ML-P.