This was a small circuit made for driving an Impact counter. The heart being ICL8038. It must have been a Motor driving a Conveyor, the motor has a feedback attachment called Tachogenerator.
Tacho Counter for Speed and Quantity Measurement
Only part of the circuit is shown here. See the image of product here Tacho Counter. The configuration is derived from the Application Notes of Intersil. The Voltage from Tachogenerator is Measured on a DPM-DVM and also fed to this circuit after attenuation and filtering.
Function Generator using ICL8038.
The square pulses of 8038 is used to derive a Logic pulse train for a CD4040. The CD4040 works of 0 and 12V. The above circuit is on +12 and -12. That is the reason R10-R15-Q1 are used. The pulses are 0-12V pulses. The Zero is Virtual like the Virtual Ground in low current power supplies.
See in magazine above a Phototach evolved from an urgent need to accurately measure the maximum propeller rpm "revolutions per minute" of an experimental aircraft. That rpm was the sole indicator of engine output, but the tachometer used to measure it was suffering from vibration-induced fatigue and its readings were more than .....