Abstract: An electrical circuit comprising means for receiving an input signal for encoding or modulating and amplification. Multiple amplification stages including at least one transconductance amplifier are provided. There are means for having the input signal modulate the oscillator constituted by the multiple amplification stages to provide a 360.degree. phase-shifted signal at a predetermined frequency. Gain control means are also provided for developing level for permitting oscillation under conditions including at least the conditions of turn on of the circuit and other operating conditions. The gain control means includes a transistor and resistor network for adjusting the gain to sustain the oscillation. The transistor and resistor also regulate amplification of an intermediate stage of the amplifier. The preamplifier directly converts an EKG and/or other signals to linearized control currents which modulate the oscillator.