Microphone Model 705


The Ten-Tec Model 705 is an Electret desk microphone designed for use as a station microphone in commercial and amateur radio communications and in public address and paging installations. The microphone consists of a base section and flexible gooseneck mounted microphone. The Model 705 incorporates a momentary type Push-To-Talk (PTT) button (gray), a Push-On, Push-Off locking type button (black), electronic circuitry to switch the microphone on, a signal amplifier that adds 13 dB of gain to the output level, an attached output cable and a battery compartment for a 9 volt alkaline battery. The PTT circuitry allows switching transmitters and/or transceivers, that have a low voltage positive T/R lines, into transmit mode. A light emitting diode in the base signals the transmit mode.

The Model 705 comes in two versions. The standard unit includes a four pin standard locking type cable connector which is pin compatible with Ten-Tec Models 560, 561, 562, 563, 564 and 585. With a minor resistor change in the Models 560 and 561, the standard unit may be powered from the transceiver without the need for a 9 volt battery. The Model 705-A comes with a stereo 1/4" phone plug. This unit is compatible with the Ten-Tec Models 525, 540, 544, 515, and other early models. A 9 volt battery is required for the Model 705-A.

Difference Between the 705 and 706

The 705 and 706 are essentially the same. The 706 does not have the compartment in the bottom to hold a 9V battery to supply voltage for the electret mic and circuitry. The 706 only works with rigs that supply the necessary voltage through the mic connector whereas the 705 can operate from rig voltage or battery. Also the 705 has a switch on the bottom to tell the controls on the mike base if you operate VOX or PTT. The 705 has a bit more versatility for use with older transceivers not having voltage present at the mic connector for the electret mic.

Corsair Modification

The documentation that accompanied the 705 microphone included information on modifying a Corsair I or early Corsair II (s/n before 1970) to power the 705 microphone. The modification involves shunting an existing 10K ohm resistor on the IF/AF board with a 470 ohm 1/2w resistor.

Mods & Tips


  • Type: Electret Condenser Microphone.
  • Sensitivity: -52 dBV (0 dBV = 1 V/uBar @ 1 kHz).
  • Output Impedance: Works with any circuit of 100 ohms or more.
  • Maximum Sound Pressure Level: 130 dB
  • Battery Type: 9 volt Alkaline transistor battery.
  • Electronics: C-Mos PTT switch, C-Mos signal amplifier, NPN T/R transistor.
  • Current Required: Receive mode: Less than 2 microamperes. Transmit mode: 2 milliamperes typical, with 9 volt battery.
  • Semiconductors: 2 IC's; 1 Transistor; 7 Diodes.
  • Weight: 12 oz. including battery.

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