> 4.5 | Galvanic Coupling of the Speaker Signal

> The GSM module is able to directly drive speakers. The frequency response and loudness largely depends on the measurement method, casing, fitting and impedance. An impedance of 8Ω at interface 1 and 32Ω at interface 2 is recommended. The outputs of the modules listed in Section 1.1 are not short circuit protected.
> Figure 16 shows a sample circuit of speakers directly connected to the GSM module. C8 and C9 as well as D2 and D3 protect the module from ESD pulses. Ferrite beads L2 and L3 are recommended to protect the EP lines from the RF signal being caught by the speaker.
> Figure 17: Sample of a module output driving a speaker