From the 1968 Shure Microphone Catalog:
General: Model “510” series Controlled Magnetic Microphones are pressure operated magnetic units using the Balanced-armature Controlled Magnetic principle. The microphones have high impedance, high output, smooth response and a semi-directional pickup characteristic. The stability of these microphones is assured by unique control of the reluctance of the magnetic system. High impedance is obtained without the use of a transformer. The Model “510” series microphones have a sturdy die-cast case.
The models 510c and 510s are suitable for placement on a table top, desk top, or other flat surface; they fit conveniently in the palm of the hand for use as a hand microphone. The micro-phones are provided with a stand adapter having a 5-27 thread which fits the conventional floor stand. The adapter attaches to the base of the microphone by using the # 8-32 machine screw pro¬vided. Model 510S has a built in switch to control the microphone circuit. Model 510c has no switch.
Each of the microphones in the “510” series is provided with a 7-foot (2.1 m) single conductor, shielded cable.
Applications: Model “510c” series microphones provide the ruggedness, the clear reproduction, and the high output needed in many applications.
These microphones may be used in fixed and mobile public address systems (including carnivals, circuses, parking lots, paging systems, etc.), communications, dictating machines, portable recording machines, home recording, language lab sys¬tems and high quality inter-communication.
These microphones are unusally rugged and are practically immune to severe moisture and temperature conditions-which makes them especially ideal for use in tropical and coastal areas. Also, the Model “510” series microphones may be used in applications requiring a soft speaker or receiver.
Connections: The microphones may be used with any public address amplifier or other amplifier with an input impedance of 100,000 ohms or more.
The inner or “hot” conductor of the cable should be connected to the grid of the first tube in the amplifier across a load resistance of I 00,DDD ohms or more. The shield should be connected to the chassis or amplifier ground. The shield , chassis or amplifier ground should be securely grounded to a water pipe or similar ground lo prevent shock hazard during operation of the amplifying system. Cable lengths longer than 25 feet (7.6 m) will be accompanied by some loss of high frequency response.
In certain amplifiers, the grid bias is obtained by having a grid leak between grid and cathode. When such amplifiers are used with any con trolled magnetic or dynamic-type microphone, it may be necessary to include a coupling condenser between the microphone and the input grid. The condenser should be .01 mfd. or larger.
Operation: The Model 510s “Hercules” Controlled Mag¬netic Microphone has a built-in switch to control the microphone cir¬cuit. The switch is a press-to-talk locking or non-locking switch, having long-life phosphor-bronze blades with fine silver contacts. For momentary contact, depress switch button and release. For lock ing, depress switch button and slide button upward.
No special precautions beyond ordinary care are necessary in the operation of the Model “510” series microphones.
Copyright 1951, Shure Brothers Inc.
