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beginning of the project

Retro Handset For Mobile Phone

Once again here is a true recycling project – turning an yesteryear’s telephone handset into a general purpose retro handset for today’s mobile phones. Recently, I bought one piece of the trendy “mobile phone retro hansdset” from an online store. Unfortunately the cheap, chinese-made, little gizmo failed to reach up to my expectations both in physical and technical aspects. Thereafter, I leaped into this green electronics project, realized with the help of a few cannibalized components and parts.

beginning of the project

(beginning of the project)

First of all, look for and gather one telephone handset (ofcourse with its coiled-cord) from a discarded telephone. Next, ensure that mouthpiece (microphone) and earpiece (speaker) mounted inside the handle are in working condition, and keep an eye on its wiring. Usually yellow (+) and black (-) wires of the coiled-cord are for the speaker, and red (+) and green (-) wires are for the microphone, but not guaranteed. Incase of a doubt, try to open the handset carefully and take a clear note about its internal wiring, just before the starting of the actual construction.

internal wiring of the telephone handset

(internal wiring of the telephone handset)

For the 3.5mm mobile phone headset jack, fix up such an old jack with short-length of wires which can be trim down from an unused mobile headset. Now interconnect the telephone handset with the 3.5mm headset jack as shown in the final wiring diagram.

pin assignment of a standard 3.5mm headset jack

(pin assignment of a standard 3.5mm headset jack)

final wiring diagram

(final wiring diagram)

Finally, note that this is not a universal solution. In case of a mismatch* between the internal electronics of your mobile phone and the impedance/electrical properties of the transducers in your telephone handset, some discrepancies may occur. So always use this non-standard accessory at your own risk!

near-finished & tested prototype

(near-finished & tested prototype)

*Lab Findings:

  • DC resistance of the earpiece capsule (speaker) in the telephone handset is about 150 – Ohms
  • DC resistance of the earphone(s) in a typical mobile phone headset is about 32 – Ohms

7 Comments

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  • ptarantinoaspencore-com

    Great, this looks fun.

  • Dahiru

    I want to feed the output of my mixer to the phone microphone input just as I use to feed the output of the phone to the console and record the incoming calls. I believe the mixer output is large for the phone input.

    Suggest a simple way. I’ve tried feeding directly but it cuts the call most of the time. I however find the DIY retro handset useful.

  • k nagarjuna

    Comment

  • T.K.Hareendran

    In the DIYers Guide, posted here, don’be confused with the term “PTT”.

    Actually, Push to talk (PTT), is a means of instantaneous communication commonly employed in wireless cellular phone services that uses a button to switch a device from voice transmission mode to voice reception mode. The operation of phones used in this way is similar to “walkie talkie” use. PTT switches a phone from full duplex mode, where both parties can hear each other simultaneously, to half duplex mode, where only one party can speak at one time.

    Here the term simply denotes an option to answer the call just by pushing the button-switch of your retro handset (as usual with many mobile phone headsets) if your mobile phone permits such an action!

    Wanna know more about PTT? Read this: https://en.wikipedia.org/wiki/Push-to-talk

  • T.K.Hareendran

    DIYers GUIDE!

    This additional note is for those not much familiar with retro handsets and mobile phone headsets:

    1. The headphones with mic used for mobile phone applications have 4 steps. The standard configuration is either CTIA or OMTP. Refer this for more details: https://en.wikipedia.org/wiki/Phone_connector_(audio)

    2. If a button-switch is present in the mobile phone headset, usually you can use the “Push-To-Talk (PTT)” option to attend an incoming call. If you wish to incorporate this facility in your diy retro handset, try to add a push button+ resistor combination in parallel with the microphone, as shown here. If tested okay, then handily mount the push button switch at the middle of the modified retro handset (again, not working with all mobile phones)!

  • T.K.Hareendran

    Kuberkoos: Thanks 🙂

  • Kuberkoos

    Crayzeeee! :-)))

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