of 3.75 or 7.5 inches per second (ips).
At the slower speed, playing
time is twice that of the higher speed and good quality voice record-
ing can be obtained.
At higher tape speed, fidelity is improved.
Fast forward and fast rewind speeds are provided.
section of the recorder contains four main sections; the record cir-
cuits, playback circuits, a bias oscillator, and a power supply.
The tape transport section contains three drive motors (capstan, fast
forward, and fast rewind) and the mechanism required to physically
move the tape.
Refer to the block diagram, figure 4-1, and to the schematic
diagram, figure 4-2.
The record circuits contain two input jacks, one
for a microphone and one for a high impedance (bridging) input which
can be connected across a low impedance source (such as a loudspeaker
coil) with negligible loading effects.
When the microphone jack is
used, contacts of the jack open the bridging input.
Audio signals from the input jacks are amplified in the
microphone amplifier, Ql, Q2 and again in record driver Q4, to the
level required to drive the playback-record head.
The audio signals
are then applied to the head through the RECORD contacts of RECORD
A sample of the audio signals at the collector of micro-
phone amplifier Q2 is taken through R19 and amplified in meter
The amplified signal is rectified by rectifier diodes
CR1 and CR2 to produce a dc signal which fluctuates with the average
level of the audio signal peaks.
This dc signal is applied to W
(Volume Units) meter M1 to provide a measure of the record signal
Microphone preamplifier Ql, Q2 is a two stage direct coupled
R11 provides linear negative feedback to stabilize the