Rall's idealized model of a dendritic tree is sufficiently simple so that an RCG cable analysis is feasible. When numerical values are substituted, further simplification occurs because it is assumed that the width of a postsynaptic potential (PSP) is the same as the shunt C/G time constant, 4 ms. The calculation shows that if a PSP having a peak amplitude of 100 mV is launched at the extreme end of the tree, it will arrive at the neuron body having a peak amplitude of 0.4625 mV and a width of 7.5 ms. The net stimulus arriving at the neuron body can be easily approximated, no matter how complex the set of input conditions, if dendritic potentials are replaced by their equivalent rectangular pulses.

A 15-electrode totally implanted time-multiplex telemetry unit is described that is powered by two mercury cells in series. Transcutaneous radio frequency (RF) turn-on and magnetic turnoff are used to conserve battery power. The basic cycle rate is 400 Hz, channel rate 6400 Hz. The channel 16 input consists of a 200-Hz 5 mV peak-to-peak (p-p) reference signal, and a 3200-Hz sync signal is added to all channels. The unit is1.5 \times 2.5 \times 8cm in size, weighs 41 g, and draws 3.5 mA. Low-frequency cutoff is at 0.2 Hz. The output is FM with a peak deviation of 75 kHz of a 20 MHz carrier at 5 mV peak channel input. The equivalent noise input is 2.8 μV root mean square (rms). The decoder automatically locks on the reference signal square wave with the aid of an exclusive-OR gate.

An implanted physiological-signal telemetry unit for an ambulatory animal is described. It uses a single 1.35 V mercury cell, is1 \times 2.5 \times 4cm in size, and weighs 15 g. Transcutaneous RF turn-on and magnetic turn-off are used to conserve battery power. The battery can operate 175 h before replacement. An integrated circuit amplifier supplies a voltage gain of 250 over a nominal band from 0.2 Hz to over 4 kHz. With 2 mV peak input, it yields 75 kHz peak deviation of a 20 MHz carrier. Relations between frequency,Q, receiving antenna voltage, and implant coil diameter are derived. Circuits are also given for a "turn-on" device, a 20 MHz converter, and the sequential gating of three mutually perpendicular antennas to avoid dropouts as the animal moves within the cage.

Pseudorandom dot scan yields a visually tolerable smallarea flicker for low frame rate television as compared to the large-area flicker of a conventional scanning sequence. With a short-persistence phosphor, one can use 12 frames/s. With a long persistence (such as a P38), one can display 3 frames/s. The "drift illusion factors" of various scanning systems are calculated. Ifnsquare-wave generators are used to cover a rectangle,n!different scanning sequences are possible; this is applied to the scrambling of pictures. Hybrid systems, which avoid some of the disadvantages of a square-wave scan, are described. The results of an audience-reaction experiment in determining effective resolution are given.