For some areas of US, plus in some other countries, GTE was "the other phone company":
For phone collectors, this makes their products somewhat more scarce and less available. So was pleased to find a 1960s GTE desk phone (lower left in photo) that takes its rather eclectic styling cues from both US Bell-system & German phones of that era.

For Aussie phone collectors venturing out into the Pacific, GTE product can be found in 'used stores' in Manila & Honolulu as both cities are served by GTE.

One of GTE's latest iterations is the electronic wonder in lower right of picture. I love this phone as an everyday workhorse as it's a business - not residential - device, quality is higher, and Speaker mode excellent - and am pleased to note, American-made!

The GTE speakerphone will serve until the 1970's Multi-line-"Charlie's Angels"-Speakerphone (background of picture) is running

Photo uploaded.

One quirk of the Manila GTE system - at least back in the seventies - was that voices sounded really-really weak on a call! The locals seemed to happily countenance the situation (they had no choice); the wealthy one-percent - like those living in the affluent walled enclave of Forbes Park - could have phones with booster amps - just like they had booster pumps to combat Manila's chronic low water pressure!

Looking more closely at the 1970's Multi-line Speakerphone (as seen in 'Charlie's Angels' office), one can see Centrex features/instructions next to its keypad: Centrex being virtual 1970's ("Cloud") PABX created at exchange's mainframe computer by time-sharing. Wiki states there were 20m such set-ups in USA, 2m in Canada and 1m in UK.

Was just checking out "Angels on Skates"(1979) episode (for the phones not the girls) and was pleasantly surprised that this took Charlie's Angels to Venice Beach/Santa Monica which I had forgotten was a GTE enclave within AT&T Los Angeles, as can be seen in very brief shot of a bank of payphones with GTE sign!

Another very different encounter with GTE service was in a rural U.S. area in late-seventies: They must have had newer electronic branch exchange in small town: Unlike Manila, lines were loud and clear, but one could clearly hear one's dialed number - whether received from a pulse or tone dial - stored-then-forwarded (as a rapid musical 'packet' of DTMF-sounds.) While this sounded good from a techie point of view, more sophisticated AT&T would never deign to allowing such sounds to be audible!

I am in Turkey at the moment. Speakers everywhere (not just on the mosques) carry the call to prayer from 3 AM, 7 times a day, at disturbing sound levels. You need double glazing and aircon to be able to sleep. Difficult to avoid it.

Following the call, which sometimes runs for several minutes, in many places there are two DTMF "keypresses" also heard through the speakers. Since the sound seems to be distributed by radio, maybe some form of automation?

One used to be able to buy DTMF chips at Radio Shack/Tandy for utility control applications.
Not sure if they had them in Turkey?
- would be bizarre if local bazaar has them!

Thinking about the DTMF "packet" of complete number one heard on 1970's telecom, I was troubled as to how it would work if this "in-band data packet" quickly shed the trunk code (first 3 digits), then thought: "why not keep it whole until connection complete?" (a-la internet packet routing) -- therefore allowing 'decisions' to be made for most expedient routing all along the network, each step hopefully getting call closer to target - ie the final frame (last 4 digits) -- thus the 1920's Director system a precursor to present day packet routing?